| Rfc | 4465 |
|---|
| Title | Signaling Compression (SigComp) Torture Tests |
|---|
| Author | A. Surtees, M. West |
|---|
| Date | June 2006 |
|---|
| Format: | TXT, HTML |
|---|
| Status: | INFORMATIONAL |
|---|
|
Network Working Group A. Surtees
Request for Comments: 4465 M. West
Category: Informational Siemens/Roke Manor Research
June 2006
Signaling Compression (SigComp) Torture Tests
Status of This Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
This document provides a set of "torture tests" for implementers of
the Signaling Compression (SigComp) protocol. The torture tests
check each of the SigComp Universal Decompressor Virtual Machine
instructions in turn, focusing in particular on the boundary and
error cases that are not generally encountered when running
well-behaved compression algorithms. Tests are also provided for
other SigComp entities such as the dispatcher and the state handler.
Table of Contents
1. Introduction ....................................................3
2. Torture Tests for UDVM ..........................................4
2.1. Bit Manipulation ...........................................4
2.2. Arithmetic .................................................5
2.3. Sorting ....................................................7
2.4. SHA-1 ......................................................8
2.5. LOAD and MULTILOAD .........................................9
2.6. COPY ......................................................11
2.7. COPY-LITERAL and COPY-OFFSET ..............................12
2.8. MEMSET ....................................................14
2.9. CRC .......................................................15
2.10. INPUT-BITS ...............................................16
2.11. INPUT-HUFFMAN ............................................17
2.12. INPUT-BYTES ..............................................19
2.13. Stack Manipulation .......................................20
2.14. Program Flow .............................................22
2.15. State Creation ...........................................23
2.16. STATE-ACCESS .............................................26
3. Torture Tests for Dispatcher ...................................28
3.1. Useful Values .............................................28
3.2. Cycles Checking ...........................................31
3.3. Message-based Transport ...................................32
3.4. Stream-based Transport ....................................34
3.5. Input Past the End of a Message ...........................36
4. Torture Tests for State Handler ................................38
4.1. SigComp Feedback Mechanism ................................38
4.2. State Memory Management ...................................41
4.3. Multiple Compartments .....................................44
4.4. Accessing RFC 3485 State ..................................49
4.5. Bytecode State Creation ...................................50
5. Security Considerations ........................................53
6. Acknowledgements ...............................................53
7. Normative References ...........................................53
Appendix A. UDVM Bytecode for the Torture Tests ..................54
A.1. Instructions ..............................................54
A.1.1. Bit Manipulation ...................................54
A.1.2. Arithmetic .........................................55
A.1.3. Sorting ............................................55
A.1.4. SHA-1 ..............................................56
A.1.5. LOAD and MULTILOAD .................................56
A.1.6. COPY ...............................................56
A.1.7. COPY-LITERAL and COPY-OFFSET .......................57
A.1.8. MEMSET .............................................57
A.1.9. CRC ................................................57
A.1.10. INPUT-BITS ........................................57
A.1.11. INPUT-HUFFMAN .....................................58
A.1.12. INPUT-BYTES .......................................58
A.1.13. Stack Manipulation ................................58
A.1.14. Program Flow ......................................59
A.1.15. State Creation ....................................59
A.1.16. STATE-ACCESS ......................................60
A.2. Dispatcher Tests ..........................................61
A.2.1. Useful Values ......................................61
A.2.2. Cycles Checking ...................................62
A.2.3. Message-based Transport ............................62
A.2.4. Stream-based Transport .............................62
A.2.5. Input Past the End of a Message ....................63
A.3. State Handler Tests .......................................64
A.3.1. SigComp Feedback Mechanism .........................64
A.3.2. State Memory Management ............................64
A.3.3. Multiple Compartments ..............................65
A.3.4. Accessing RFC 3485 State ...........................66
A.3.5. Bytecode State Creation ............................66
1. Introduction
This document provides a set of "torture tests" for implementers of
the SigComp protocol, RFC 3320 [2]. The idea behind SigComp is to
standardize a Universal Decompressor Virtual Machine (UDVM) that can
be programmed to understand the output of many well-known compressors
including DEFLATE and LZW. The bytecode for the chosen decompressor
is uploaded to the UDVM as part of the SigComp message flow.
The SigComp User's Guide [1] gives examples of a number of different
algorithms that can be used by the SigComp protocol. However, the
bytecode for the corresponding decompressors is relatively well
behaved and does not test the boundary and error cases that may
potentially be exploited by malicious SigComp messages.
This document is divided into a number of sections, each containing a
piece of code designed to test a particular function of one of the
SigComp entities (UDVM, dispatcher, and state handler). The specific
boundary and error cases tested by the bytecode are also listed, as
are the output the code should produce and the number of UDVM cycles
that should be used.
Each test runs in the SigComp minimum decompression memory size (that
is, 2K), within the minimum number of cycles per bit (that is, 16)
and in tests where state is stored 2K state memory size is needed.
2. Torture Tests for UDVM
The following sections each provide code to test one or more UDVM
instructions. In the interests of readability, the code is given
using the SigComp assembly language: a description of how to convert
this assembly code into UDVM bytecode can be found in the SigComp
User's Guide [1].
The raw UDVM bytecode for each torture test is given in Appendix A.
Each section also lists the number of UDVM cycles required to execute
the code. Note that this figure only takes into account the cost of
executing each UDVM instruction (in particular, it ignores the fact
that the UDVM can gain extra cycles as a result of inputting more
data).
2.1. Bit Manipulation
This section gives assembly code to test the AND, OR, NOT, LSHIFT,
and RSHIFT instructions. When the instructions have a multitype
operand, the code tests the case where the multitype contains a fixed
integer value, and the case where it contains a memory address at
which the 2-byte operand value can be found. In addition, the code
is designed to test that the following boundary cases have been
correctly implemented:
1. The instructions overwrite themselves with the result of the bit
manipulation operation, in which case execution continues
normally.
2. The LSHIFT or RSHIFT instructions shift bits beyond the 2-byte
boundary, in which case the bits must be discarded.
3. The UDVM registers byte_copy_left and byte_copy_right are used to
store the results of the bit manipulation operations. Since no
byte copying is taking place, these registers should behave in
exactly the same manner as ordinary UDVM memory addresses.
at (64)
:a pad (2)
:b pad (2)
at (128)
JUMP (start) ; Jump to address 255
at (255)
:start
; The multitypes are values
; $start = 448 (first 2 bytes of AND instr)
AND ($start, 21845) ; 448 & 21845 = 320 = 0x0140
OR ($a, 42) ; 0 | 42 = 42 = 0x002a
NOT ($b) ; ~0 = 65535 = 0xffff
LSHIFT ($a, 3) ; 42 << 3 = 336 = 0x0150
RSHIFT ($b, 65535) ; 65535 >> 65535 = 0 = 0x0000
OUTPUT (64, 4) ; Output 0x0150 0000
; The multitypes are references
AND ($a, $start) ; 336 & 320 = 320 = 0x0140
OR ($a, $a) ; 320 | 320 = 320 = 0x0140
NOT ($a) ; ~320 = 65215 = 0xfebf
LSHIFT ($b, $a) ; 0 << 65215 = 0 = 0x0000
RSHIFT ($a, $b) ; 65215 >> 0 = 65215 = 0xfebf
OUTPUT (64, 4) ; Output 0xfebf 0000
END-MESSAGE (0, 0, 0, 0, 0, 0, 0)
The output of the code is 0x0150 0000 febf 0000. Executing the code
costs a total of 22 UDVM cycles.
2.2. Arithmetic
This section gives assembly code to test the ADD, SUBTRACT, MULTIPLY,
DIVIDE, and REMAINDER instructions. The code is designed to test
that the following boundary cases have been correctly implemented:
1. The instructions overwrite themselves with the result of the
arithmetic operation, resulting in continuation as if the bytes
were not bytecode.
2. The result does not lie between 0 and 2^16 - 1 inclusive, in
which case it must be taken modulo 2^16.
3. The divisor in the DIVIDE or REMAINDER instructions is 0 (in
which case decompression failure must occur).
at (64)
:a pad (2)
:b pad (2)
:type pad (1)
:type_lsb pad (1)
at (128)
INPUT-BYTES (1, type_lsb, decomp_failure)
SUBTRACT ($type, 1)
JUMP (start)
:decomp_failure
DECOMPRESSION-FAILURE
; Now the value in $type should be 0xffff, 0x0000, or 0x0001
; according to whether the input was 0x00, 0x01, or 0x02.
at (255)
:start
; The multitypes are values
; For all three messages
; $start = 1728 (first 2 bytes of ADD instr)
ADD ($start, 63809) ; 1728 + 63809 = 1 = 0x0001
SUBTRACT ($a, 1) ; 0 - 1 = 65535 = 0xffff
MULTIPLY ($a, 1001) ; 65535 * 1001 = 64535 = 0xfc17
DIVIDE ($a, 101) ; 64535 / 101 = 638 = 0x027e
REMAINDER ($a, 11) ; 638 % 11 = 0 = 0x0000
OUTPUT (64, 4) ; output 0x0000 0000
; The multitypes are references
ADD ($b, $start) ; 0 + 1 = 1 = 0x0001
; If the message is 0x00
SUBTRACT ($b, $type) ; 1 - 65535 = 2 = 0x0002
MULTIPLY ($b, $b) ; 2 * 2 = 4 = 0x0004
DIVIDE ($a, $b) ; 0 / 4 = 0 = 0x0000
REMAINDER ($b, $type) ; 4 % 65535 = 4 = 0x0004
OUTPUT (64, 4) ; output 0x0000 0004
; If the message is 0x01, $type = 0
; so decompression failure occurs at
; REMAINDER ($b, $type)
; If the message is 0x02, $type = 1 so
; $b becomes 0 and decompression failure
; occurs at DIVIDE ($a, $b)
END-MESSAGE (0, 0, 0, 0, 0, 0, 0)
If the compressed message is 0x00, then the output of the code is
0x0000 0000 0000 0004 and the execution cost should be 25 UDVM
cycles. However, if the compressed message is 0x01 or 0x02, then
decompression failure occurs.
2.3. Sorting
This section gives assembly code to test the SORT-ASCENDING and SORT-
DESCENDING instructions. The code is designed to test that the
following boundary cases have been correctly implemented:
1. The sorting instructions sort integers with the same value, in
which case the original ordering of the integers must be
preserved.
at (128)
SORT-DESCENDING (256, 2, 23)
SORT-ASCENDING (256, 2, 23)
OUTPUT (302, 45)
END-MESSAGE (0, 0, 0, 0, 0, 0, 0)
at (256)
word (10, 10, 17, 7, 22, 3, 3, 3, 19, 1, 16, 14, 8, 2, 13, 20, 18,
23, 15, 21, 12, 6, 9)
word (28263, 8297, 30057, 8308, 26996, 11296, 31087, 29991, 8275,
18031, 28263, 24864, 30066, 29284, 28448, 29807, 28206, 11776, 28773,
28704, 28276, 29285, 28265)
The output of the code is 0x466f 7264 2c20 796f 7527 7265 2074 7572
6e69 6e67 2069 6e74 6f20 6120 7065 6e67 7569 6e2e 2053 746f 7020 6974
2e, and the number of cycles required is 371.
2.4. SHA-1
This section gives assembly code to test the SHA-1 instruction. The
code performs four tests on the SHA-1 algorithm itself and, in
addition, checks the following boundary cases specific to the UDVM:
1. The input string for the SHA-1 hash is obtained by byte copying
over an area of the UDVM memory.
2. The SHA-1 hash overwrites its own input string.
at (64)
:byte_copy_left pad (2)
:byte_copy_right pad (2)
:hash_value pad (20)
at (128)
SHA-1 (test_one, 3, hash_value)
OUTPUT (hash_value, 20)
SHA-1 (test_two, 56, hash_value)
OUTPUT (hash_value, 20)
; Set up a 1-byte buffer
LOAD (byte_copy_left, test_three)
LOAD (byte_copy_right, test_four)
; Perform SHA-1 over 16384 bytes in a 1-byte buffer
SHA-1 (test_three, 16384, hash_value)
OUTPUT (hash_value, 20)
; Set up an 8-byte buffer
LOAD (byte_copy_left, test_four)
LOAD (byte_copy_right, test_end)
; Perform SHA-1 over 640 bytes in an 8-byte buffer
SHA-1 (test_four, 640, test_four)
OUTPUT (test_four, 20)
END-MESSAGE (0, 0, 0, 0, 0, 0, 0)
:test_one
byte (97, 98, 99)
:test_two
byte (97, 98, 99, 100, 98, 99, 100, 101, 99, 100, 101, 102, 100, 101,
102, 103, 101, 102, 103, 104, 102, 103, 104, 105, 103, 104, 105, 106,
104, 105, 106, 107, 105, 106, 107, 108, 106, 107, 108, 109, 107, 108,
109, 110, 108, 109, 110, 111, 109, 110, 111, 112, 110, 111, 112, 113)
:test_three
byte (97)
:test_four
byte (48, 49, 50, 51, 52, 53, 54, 55)
:test_end
The output of the code is as follows:
0xa999 3e36 4706 816a ba3e 2571 7850 c26c 9cd0 d89d
0x8498 3e44 1c3b d26e baae 4aa1 f951 29e5 e546 70f1
0x12ff 347b 4f27 d69e 1f32 8e6f 4b55 73e3 666e 122f
0x4f46 0452 ebb5 6393 4f46 0452 ebb5 6393 4f46 0452
Executing the code costs a total of 17176 UDVM cycles.
2.5. LOAD and MULTILOAD
This section gives assembly code to test the LOAD and MULTILOAD
instructions. The code is designed to test the following boundary
cases:
1. The MULTILOAD instruction overwrites itself or any of its
operands, in which case decompression failure occurs.
2. The memory references of MULTILOAD instruction operands are
evaluated step-by-step rather than all at once before starting to
copy data.
at (64)
:start pad (1)
:start_lsb pad (1)
at (128)
set (location_a, 128)
set (location_b, 132)
LOAD (128, 132) ; address 128 contains 132 = 0x0084
LOAD (130, $location_a) ; address 130 contains 132 = 0x0084
LOAD ($location_a, 134) ; address 132 contains 134 = 0x0086
LOAD ($location_b, $location_b) ; address 134 contains 134 = 0x0086
OUTPUT (128, 8) ; output 0x0084 0084 0086 0086
INPUT-BYTES (1, start_lsb, decompression_failure)
MULTIPLY ($start, 2)
ADD ($start, 60)
MULTILOAD ($start, 3, overlap_start, overlap_end, 128)
:position
set (overlap_start, (position - 7))
MULTILOAD ($start, 4, 42, 128, $location_a, $location_b)
:end
set (overlap_end, (end - 1))
OUTPUT (128, 8)
END-MESSAGE (0, 0, 0, 0, 0, 0, 0)
:decompression_failure
DECOMPRESSION-FAILURE
The INPUT-BYTES, MULTIPLY, and ADD instructions give the following
values for $start = $64 just before the MULTILOADs begin:
Input $start before 1st MULTILOAD
0x00 60
0x01 62
0x02 64
Consequently, after the first MULTILOAD the values of $start are the
following:
Input $start before 2nd MULTILOAD
0x00 128
0x01 overlap_end = 177 = last byte of 2nd MULTILOAD instruction
0x02 overlap_start = 162 = 7 bytes before 2nd MULTILOAD
instruction
Consequently, execution of the 2nd MULTILOAD (and any remaining code)
gives the following:
Input Outcome
0x00 MULTILOAD reads and writes operand by operand. The output is
0x0084 0084 0086 0086 002a 0080 002a 002a, and the cost of
executing the code is 36 UDVM cycles.
0x01 The first write of the MULTILOAD instruction would overwrite
the last byte of the final MULTILOAD operand, so
decompression failure occurs.
0x02 The last write of the MULTILOAD would overwrite the MULTILOAD
opcode, so decompression failure occurs.
2.6. COPY
This section gives assembly code to test the COPY instruction. The
code is designed to test that the following boundary cases have been
correctly implemented:
1. The COPY instruction copies data from both outside the circular
buffer and inside the circular buffer within the same operation.
2. The COPY instruction performs byte-by-byte copying (i.e., some of
the later bytes to be copied are themselves written into the UDVM
memory by the COPY instruction currently being executed).
3. The COPY instruction overwrites itself and continues executing.
4. The COPY instruction overwrites the UDVM registers byte_copy_left
and byte_copy_right.
5. The COPY instruction writes to and reads from the right of the
buffer beginning at byte_copy_right.
6. The COPY instruction implements byte copying rules when the
destination wraps around the buffer.
at (64)
:byte_copy_left pad (2)
:byte_copy_right pad (2)
at (128)
; Set up buffer between addresses 64 & 128
LOAD (32, 16384)
LOAD (byte_copy_left, 64)
LOAD (byte_copy_right, 128)
COPY (32, 128, 33) ; Copy byte by byte starting to the left of
; the buffer, into the buffer and wrapping
; the buffer (inc overwriting the
; boundaries)
LOAD (64, 16640) ; Change the start of the buffer to be
; beyond bytecode
COPY (64, 85, 65) ; Copy to the left of the buffer,
; overwriting this instruction
OUTPUT (32, 119) ; Output 32 * 0x40 + 86 * 0x41 + 0x55,
; which is 32 * '@' + 86 'A' + 'U'
; Set a new small buffer
LOAD (byte_copy_left, 32)
LOAD (byte_copy_right, 48)
MEMSET (32, 4, 65, 1) ; Set first 4 bytes of the buffer to be
; 'ABCD'
COPY (32, 4, 48) ; Copy from byte_copy_right (i.e., not
; in buffer)
OUTPUT (48, 4) ; Output 0x4142 4344, which is 'ABCD'
COPY (48, 4, 46) ; Copy from two before byte_copy_right to
; wrap around the buffer
OUTPUT (32, 2) ; Output 0x4344, which is 'CD'
END-MESSAGE (0, 0, 0, 0, 0, 0, 0)
The output is above, and executing the code costs a total of 365 UDVM
cycles.
2.7. COPY-LITERAL and COPY-OFFSET
This section gives assembly code to test the COPY-LITERAL and COPY-
OFFSET instructions. The code is designed to test similar boundary
cases to the code for the COPY instruction, as well as the following
condition specific to COPY-LITERAL and COPY-OFFSET:
1. The COPY-LITERAL or COPY-OFFSET instruction overwrites the value
of its destination.
2. The COPY-OFFSET instruction reads from an offset that wraps
around the buffer (i.e., the offset is larger than the distance
between byte_copy_left and the destination).
at (64)
:byte_copy_left pad (2)
:byte_copy_right pad (2)
:destination pad (2)
:offset pad (2)
at (128)
; Set up circular buffer, source, and
; destination
LOAD (32, 16640)
LOAD (byte_copy_left, 64)
LOAD (byte_copy_right, 128)
LOAD (destination, 33)
COPY-LITERAL (32, 128, $destination) ; Copy from the left of the
; buffer overwriting bcl, bcr, and
; destination wrapping around the buffer
OUTPUT (64, 8) ; Check destination has been updated
; Output 0x4141 4141 0061 4141
LOAD (destination, copy)
:copy ; Overwrite the copy instruction
COPY-LITERAL (32, 2, $destination)
OUTPUT (copy, 2) ; Output 0x4141
LOAD (byte_copy_left, 72) ; Set up new circular buffer
LOAD (byte_copy_right, 82)
LOAD (destination, 82) ; Set destination to byte_copy_right
MEMSET (72, 10, 65, 1) ; Fill the buffer with 0x41 - 4A
COPY-OFFSET (2, 6, $destination) ; Copy from within circular
; buffer to outside buffer
LOAD (offset, 6)
COPY-OFFSET ($offset, 4, $destination)
; Copy from byte_copy_right
; so reading outside buffer
OUTPUT ($byte_copy_right, 10) ; Output 0x494A 4142 4344 494A 4142,
; which is 'IJABCDIJAB'
LOAD (destination, 80) ; Put destination within the
; buffer
COPY-OFFSET (4, 4, $destination) ; Copy where destination wraps
OUTPUT (destination, 2) ; Output 0x004A
COPY-OFFSET (5, 4, $destination) ; Copy where offset wraps from
; left back around to the right
OUTPUT (destination, 2) ; Output 0x004E
OUTPUT ($byte_copy_left, 10) ; Output the circular buffer
; 0x4748 4845 4647 4748 4546,
; which is 'GHHEFGGHEF'
END-MESSAGE (0, 0, 0, 0, 0, 0, 0)
The output of the code is above, and the cost of execution is 216
UDVM cycles.
2.8. MEMSET
This section gives assembly code to test the MEMSET instruction. The
code is designed to test that the following boundary cases have been
correctly implemented:
1. The MEMSET instruction overwrites the registers byte_copy_left
and byte_copy_right.
2. The output values of the MEMSET instruction do not lie between 0
and 255 inclusive (in which case they must be taken modulo 2^8).
at (64)
:byte_copy_left pad (2)
:byte_copy_right pad (2)
at (128)
LOAD (byte_copy_left, 128) ; sets up a circular buffer
LOAD (byte_copy_right, 129) ; of 1 byte between 0x0080 and 0x0081
MEMSET (64, 129, 0, 1) ; fills up the memory in the range
; 0x0040-0x007f with 0x00, ... 0x3f;
; then it writes successively at
; 0x0080 the following values 0x40, ... 0x80
; as a side effect, the values of
; bcl and bcr are modified.
; before and during the MEMSET:
; byte_copy_left: 0x0080 byte_copy_right: 0x0081
; after the MEMSET:
; byte_copy_left: 0x0001 byte_copy_right: 0x0203
MEMSET (129, 15, 64, 15) ; fills the memory range 0x0080-0x008f
; with values 0x40, 0x4f, ... 0xf4, 0x03, 0x12.
; as a side effect, it overwrites a
; part of the code including itself
OUTPUT (128, 16) ; outputs 0x8040 4f5e 6d7c 8b9a
; a9b8 c7d6 e5f4 0312
END-MESSAGE (0, 0, 0, 0, 0, 0, 0)
The output of the code is 0x8040 4f5e 6d7c 8b9a a9b8 c7d6 e5f4 0312.
Executing the code costs 166 UDVM cycles.
2.9. CRC
This section gives assembly code to test the CRC instruction. The
code does not test any specific boundary cases (as there do not
appear to be any) but focuses instead on verifying the CRC algorithm.
at (64)
:byte_copy_left pad (2)
:byte_copy_right pad (2)
:crc_value pad (2)
:crc_string_a pad (24)
:crc_string_b pad (20)
at (128)
MEMSET (crc_string_a, 24, 1, 1) ; sets up between 0x0046 and 0x005d
; a byte string containing 0x01,
; 0x02, ... 0x18
MEMSET (crc_string_b, 20, 128, 1) ; sets up between 0x005e and 0x0071
; a byte string containing 0x80,
; 0x81, ... 0x93
INPUT-BYTES (2, crc_value, decompression_failure)
; reads in 2 bytes representing
; the CRC value of the byte string
; of 44 bytes starting at 0x0046
CRC ($crc_value, crc_string_a, 44, decompression_failure)
; computes the CRC value of the
; byte string crc_string_a
; concatenated with byte string
; crc_string_b (with a total
; length of 44 bytes).
; if the computed value does
; not match the 2-byte value read
; previously, the program ends
; with DECOMPRESSION-FAILURE.
END-MESSAGE (0, 0, 0, 0, 0, 0, 0)
:decompression_failure
DECOMPRESSION-FAILURE
If the compressed message is 0x62cb, then the code should
successfully terminate with no output, and with a total execution
cost of 95 UDVM cycles. For different 2-byte compressed messages,
the code should terminate with a decompression failure.
2.10. INPUT-BITS
This section gives assembly code to test the INPUT-BITS instruction.
The code is designed to test that the following boundary cases have
been correctly implemented:
1. The INPUT-BITS instruction changes between any of the four
possible bit orderings defined by the input_bit_order register.
2. The INPUT-BITS instruction inputs 0 bits.
3. The INPUT-BITS instruction requests data that lies beyond the end
of the compressed message.
at (64)
:byte_copy_left pad (2)
:byte_copy_right pad (2)
:input_bit_order pad (2)
:result pad (2)
at (128)
:start
INPUT-BITS ($input_bit_order, result, end_of_message) ; reads in
; exactly as many bits as the 2-byte
; value written in the input_bit_order
; register, get out of the loop when
; no more bits are available at input.
OUTPUT (result, 2) ; outputs as a 2-byte integer
; the previously read bits
ADD ($input_bit_order, 1) ; if at the beginning of this loop the
; register input_bit_order is 0,
REMAINDER ($input_bit_order, 7) ; then its value varies periodically
; like this: 2, 4, 6, 1, 3, 5, 7.
ADD ($input_bit_order, 1) ; that gives for the FHP bits: 010,
; 100, 110, 001, 011, 101, 111
JUMP (start) ; run the loop once more
:end_of_message
END-MESSAGE (0, 0, 0, 0, 0, 0, 0)
An example of a compressed message is 0x932e ac71, which decompresses
to give the output 0x0000 0002 0002 0013 0000 0003 001a 0038.
Executing the code costs 66 UDVM cycles.
2.11. INPUT-HUFFMAN
This section gives assembly code to test the INPUT-HUFFMAN
instruction. The code is designed to test that the following
boundary cases have been correctly implemented:
1. The INPUT-HUFFMAN instruction changes between any of the four
possible bit orderings defined by the input_bit_order register.
2. The INPUT-HUFFMAN instruction inputs 0 bits.
3. The INPUT-HUFFMAN instruction requests data that lies beyond the
end of the compressed message.
at (64)
:byte_copy_left pad (2)
:byte_copy_right pad (2)
:input_bit_order pad (2)
:result pad (2)
at (128)
:start
INPUT-HUFFMAN (result, end_of_message, 2, $input_bit_order, 0,
$input_bit_order, $input_bit_order, $input_bit_order, 0, 65535, 0)
OUTPUT (result, 2)
ADD ($input_bit_order, 1)
REMAINDER ($input_bit_order, 7)
ADD ($input_bit_order, 1)
JUMP (start)
:end_of_message
END-MESSAGE (0, 0, 0, 0, 0, 0, 0)
An example of a compressed message is 0x932e ac71 66d8 6f, which
decompresses to give the output 0x0000 0003 0008 04d7 0002 0003 0399
30fe. Executing the code costs 84 UDVM cycles.
As the code is run, the input_bit_order changes through all possible
values to check usage of the H and P bits. The number of bits to
input each time is taken from the value of input_bit_order. The
sequence is the following:
Input_bit_order (bin) Total bits input by Huffman Value
000 0 0
010 2 3
100 4 8
110 12 1239
001
P-bit changed, throw away 6 bits
001 1 2
011 3 3
101 10 921
111 14 12542
010
P-bit changed, throw away 4 bits
010 0 - not enough bits so terminate
2.12. INPUT-BYTES
This section gives assembly code to test the INPUT-BYTES instruction.
The code is designed to test that the following boundary cases have
been correctly implemented:
1. The INPUT-BYTES instruction inputs 0 bytes.
2. The INPUT-BYTES instruction requests data that lies beyond the
end of the compressed message.
3. The INPUT-BYTES instruction is used after part of a byte has been
input (e.g., by the INPUT-BITS instruction).
at (64)
:byte_copy_left pad (2)
:byte_copy_right pad (2)
:input_bit_order pad (2)
:result pad (2)
:output_start pad (4)
:output_end
at (128)
LOAD (byte_copy_left, output_start)
LOAD (byte_copy_right, output_end)
:start
INPUT-BITS ($input_bit_order, result, end_of_message)
OUTPUT (result, 2)
ADD ($input_bit_order, 2)
REMAINDER ($input_bit_order, 7)
INPUT-BYTES ($input_bit_order, output_start, end_of_message)
OUTPUT (output_start, $input_bit_order)
ADD ($input_bit_order, 1)
JUMP (start)
:end_of_message
END-MESSAGE (0, 0, 0, 0, 0, 0, 0)
An example of a compressed message is 0x932e ac71 66d8 6fb1 592b dc9a
9734 d847 a733 874e 1bcb cd51 b5dc 9659 9d6a, which decompresses to
give the output 0x0000 932e 0001 b166 d86f b100 1a2b 0003 9a97 34d8
0007 0001 3387 4e00 08dc 9651 b5dc 9600 599d 6a. Executing the code
costs 130 UDVM cycles.
As the code is run, the input_bit_order changes through all possible
values to check usage of the F and P bits. The number of bits or
bytes to input each time is taken from the value of input_bit_order.
For each INPUT-BYTES instruction, the remaining bits of the byte are
thrown away. The P-bit always changes on the byte boundary so no
bits are thrown away. The sequence is the following:
Input_bit_order (bin) Input bits Input bytes Output
000 0 0x0000
010 2 0x932e
011 3 0x0001
101 5 0xb166 d866 b1
110 6 0x001a
001 1 0x2b
010 2 0x0003
100 4 0x9a97 34d8
101 5 0x0007
000 0
001 1 0x0001
011 3 0x3384 4e
100 4 0x0008
110 6 0xdc96 51b5 dc96
111 7 0x0059
010 2 0x9d6a
011 3 - no bits left so terminate
2.13. Stack Manipulation
This section gives assembly code to test the PUSH, POP, CALL, and
RETURN instructions. The code is designed to test that the following
boundary cases have been correctly implemented:
1. The stack manipulation instructions overwrite the UDVM register
stack_location.
2. The CALL instruction specifies a reference operand rather than an
absolute value.
3. The PUSH instruction pushes the value contained in stack_fill
onto the stack.
4. The stack_location register contains an odd integer.
at (64)
:byte_copy_left pad (2)
:byte_copy_right pad (2)
:input_bit_order pad (2)
:stack_location pad (2)
:next_address pad (2)
at (128)
LOAD (stack_location, 64)
PUSH (2)
PUSH ($64)
PUSH (66) ; Stack now contains 2, 1, 66
; so $stack_location = 66
OUTPUT (64, 8) ; Output 0x0003 0002 0001 0042
POP (64) ; Pop value 66 from address 70 to address 64
POP ($stack_location) ; Pop value 1 from address 68 to address 66
; so stack_fill is overwritten to be 1
POP (stack_location) ; Pop value 1 from address 68 to address 70
OUTPUT (64, 8) ; Output 0x0042 0000 0001 0001
JUMP (address_a)
at (192)
:address_a
LOAD (stack_location, 32)
LOAD (next_address, address_c)
SUBTRACT ($next_address, address_b) ; next_address = 64
CALL (address_b) ; push 204 on stack
at (256)
:address_b
CALL ($next_address) ; push 256 on stack
at (320)
:address_c
LOAD (stack_location, 383)
LOAD (383, 26) ; overwrite $stack_location with 26
MULTILOAD (432, 3, 1, 49153, 32768)
; write bytes so that 433 and 434
; contain 0x01c0 = 448 and
; 435 and 436 contain 0x0180 = 384
RETURN ; pop 383 from the stack and jump
; there = 384, which is lsb of
; stack_fill, which now contains 25,
; which is UDVM instruction RETURN
; pop 448 from the stack and jump
; there
at (448)
END-MESSAGE (0, 0, 0, 0, 0, 0, 0)
The output of the code is 0x0003 0002 0001 0042 0042 0000 0001 0001,
and a total of 40 UDVM cycles are used.
2.14. Program Flow
This section gives assembly code to test the JUMP, COMPARE, and
SWITCH instructions. The code is designed to test that the following
boundary cases have been correctly implemented:
1. The address operands are specified as references to memory
addresses rather than as absolute values.
at (64)
:next_address pad (2)
:counter pad (1)
:counter_lsb pad (1)
:switch_counter pad (2)
at (128)
LOAD (switch_counter, 4)
:address_a
LOAD (next_address, address_c)
SUBTRACT ($next_address, address_b) ; address_c - address_b
OUTPUT (counter_lsb, 1)
:address_b
JUMP ($next_address) ; Jump to address_c
:address_c
ADD ($counter, 1)
LOAD (next_address, address_a)
SUBTRACT ($next_address, address_d) ; address_a - address_d
OUTPUT (counter_lsb, 1)
:address_d
COMPARE ($counter, 6, $next_address, address_c, address_e)
; counter < 6, $next_address gives
; jump to address_a
:address_e
SUBTRACT ($switch_counter, 1) ; switch_counter = 3
LOAD (next_address, address_a)
SUBTRACT ($next_address, address_f) ; address_a - address_f
OUTPUT (counter_lsb, 1)
:address_f
SWITCH (4, $switch_counter, address_g, $next_address, address_c,
address_e)
; when $switch_counter = 1,
; $next_address gives jump to
; address_a
:address_g
END-MESSAGE (0, 0, 0, 0, 0, 0, 0)
The output of the code is 0x0001 0102 0203 0304 0405 0506 0707 0708
0808 0909, and a total of 131 UDVM cycles are used.
2.15. State Creation
This section gives assembly code to test the STATE-CREATE and STATE-
FREE instructions. The code is designed to test that the following
boundary cases have been correctly implemented:
1. An item of state is created that duplicates an existing state
item.
2. An item of state is freed when the state has not been created.
3. An item of state is created and then freed by the same message.
4. The STATE-FREE instruction frees a state item by sending fewer
bytes of the state_identifier than the minimum_access_length.
5. The STATE-FREE instruction has partial_identifier_length operand
shorter than 6 or longer than 20.
6. The STATE-FREE instruction specifies a partial_identifier that
matches with two state items in the compartment.
7. The bytes of the identifier are written to the position specified
in the STATE-FREE instruction after the STATE-FREE instruction
has been run (and before END-MESSAGE).
at (64)
:byte_copy_left pad (2)
:byte_copy_right pad (2)
:states pad (1)
:states_lsb pad (1)
:min_len pad (1)
:min_len_lsb pad (1)
:state_identifier pad (20)
set (state_length, 10)
at (127)
:decompression_failure
at (128)
INPUT-BYTES (1, states_lsb, decompression_failure)
:test_one
LSHIFT ($states, 11)
COMPARE ($states, 32768, test_two, create_state_a2, create_state_a2)
:create_state_a2
STATE-CREATE (state_length, state_address2, 0, 20, 0)
:test_two
LSHIFT ($states, 1)
COMPARE ($states, 32768, test_three, create_state_a, create_state_a)
:create_state_a
STATE-CREATE (state_length, state_address, 0, 20, 0)
:test_three
LSHIFT ($states, 1)
COMPARE ($states, 32768, test_four, free_state, free_state)
:free_state
INPUT-BYTES (1, min_len_lsb, decompression_failure)
STATE-FREE (state_identifier, $min_len)
COPY (identifier1, $min_len, state_identifier)
:test_four
LSHIFT ($states, 1)
COMPARE ($states, 32768, test_five, free_state2, free_state2)
:free_state2
STATE-FREE (identifier1, 6)
:test_five
LSHIFT ($states, 1)
COMPARE ($states, 32768, end, create_state_b, create_state_b)
:create_state_b
END-MESSAGE (0, 0, state_length, state_address, 0, 20, 0)
:end
END-MESSAGE (0, 0, 0, 0, 0, 0, 0)
:identifier1
byte (67, 122, 232, 10, 15, 220, 30, 106, 135, 193, 182, 42, 118,
118, 185, 115, 49, 140, 14, 245)
at (256)
:state_address
byte (192, 204, 63, 238, 121, 188, 252, 143, 209, 8)
:state_address2
byte (101, 232, 3, 82, 238, 41, 119, 23, 223, 87)
Upon reaching the END-MESSAGE instruction, the UDVM does not output
any decompressed data, but instead may make one or more state
creation or state free requests to the state handler. Assuming that
the application does not veto the state creation request (and that
sufficient state memory is available) the code results in 0, 1, or 2
state items being present in the compartment.
The following table lists ten different compressed messages, the
states created and freed by each, the number of states left after
each message, and the number of UDVM cycles used. There are 3 state
creation instructions:
create state_a, which has hash identifier1
create state_b (in END-MESSAGE), which is identical to state_a
create state_a2, which has a different identifier, but the first 6
bytes are the same as those of identifier1.
Message: Effect: # state items: #cycles:
0x01 create state_b 1 23
0x02 free (id1, 6) = state_b 0 14
0x03 free (id1, 6) = state_b; create state_b 1 24
0x0405 free (id1, 5) Decompression failure
0x0415 free (id1, 21) Decompression failure
0x0406 free (id1, 6) = state_b 0 23
0x09 create state_a; create state_b 1 34
0x1e06 create state_a2; create state_a;
free (id1, 6) = matches both so no free;
free (id1, 6) = matches both so no free; 2 46
0x1e07 create state_a2; create state_a;
free (id1, 7) = state_a;
free (id1, 6) = state_a2 0 47
0x1e14 create state_a2; create state_a;
free (id1, 20) = state_a;
free (id1, 6) = state_a2 0 60
2.16. STATE-ACCESS
This section gives assembly code to test the STATE-ACCESS
instruction. The code is designed to test that the following
boundary cases have been correctly implemented:
1. A subset of the bytes contained in a state item is copied to the
UDVM memory.
2. Bytes are copied from beyond the end of the state value.
3. The state_instruction operand is set to 0.
4. The state cannot be accessed because the partial state identifier
is too short.
5. The state identifier is overwritten by the state item being
accessed.
The following bytecode needs to be run first to set up the state for
the rest of the test.
at (128)
END-MESSAGE (0, 0, state_length, state_start, 0, 20, 0)
; The bytes between state_start and state_end are derived from
; translation of the following mnemonic code:
;
; at (512)
; OUTPUT (data, 4)
; END-MESSAGE (0,0,0,0,0,0,0)
; :data
; byte (116, 101, 115, 116)
at (512)
:state_start
byte (34, 162, 12,4, 35, 0, 0, 0, 0, 0, 0, 0, 116, 101, 115, 116)
:state_end
set (state_length, (state_end - state_start))
This is the bytecode for the rest of the test.
at (64)
:byte_copy_left pad (2)
:byte_copy_right pad (2)
:type pad (1)
:type_lsb pad (1)
:state_value pad (4)
at (127)
:decompression_failure
at (128)
INPUT-BYTES (1, type_lsb, decompression_failure)
COMPARE ($type, 1, execute_state, extract_state, error_conditions)
:execute_state
STATE-ACCESS (state_identifier, 20, 0, 0, 0, 512)
:extract_state
STATE-ACCESS (state_identifier, 20, 12, 4, state_value, 0)
OUTPUT (state_value, 4)
JUMP (end)
:error_conditions
COMPARE ($type, 3, state_not_found, id_too_short, state_too_short)
:state_not_found
STATE-ACCESS (128, 20, 0, 0, 0, 0)
JUMP (end)
:id_too_short
STATE-ACCESS (state_identifier, 19, 6, 4, state_value, 0)
JUMP (end)
:state_too_short
STATE-ACCESS (state_identifier, 20, 12, 5, state_value, 0)
JUMP (end)
at (484)
:end
END-MESSAGE (0, 0, 0, 0, 0, 0, 0)
at (512)
:state_identifier
byte (0x5d, 0xf8, 0xbc, 0x3e, 0x20, 0x93, 0xb5, 0xab, 0xe1, 0xf1,
0x70, 0x13, 0x42, 0x4c, 0xe7, 0xfe, 0x05, 0xe0, 0x69, 0x39)
If the compressed message is 0x00, then the output of the code is
0x7465 7374, and a total of 26 UDVM cycles are used. If the
compressed message is 0x01, then the output of the code is also
0x7465 7374 but in this case using a total of 15 UDVM cycles. If the
compressed message is 0x02, 0x03, or 0x04, then decompression failure
occurs.
3. Torture Tests for Dispatcher
The following sections give code to test the various functions of the
SigComp dispatcher.
3.1. Useful Values
This section gives assembly code to test that the SigComp "Useful
Values" are correctly initialized in the UDVM memory. It also tests
that the UDVM is correctly terminated if the bytecode uses too many
UDVM cycles or tries to write beyond the end of the available memory.
The code tests that the following boundary cases have been correctly
implemented:
1. The bytecode uses exactly as many UDVM cycles as are available
(in which case no problems should arise) or one cycle too many
(in which case decompression failure should occur). A liberal
implementation could allow more cycles to be used than are
strictly available, in which case decompression failure will not
occur. This is an implementation choice. If this choice is
made, the implementer must be sure that the cycles are checked
eventually and that decompression failure does occur when
bytecode uses an excessive number of cycles. This is tested in
Section 3.2.
2. The bytecode writes to the highest memory address available (in
which case no problems should arise) or to the memory address
immediately following the highest available address (in which
case decompression failure must occur).
:udvm_memory_size pad (2)
:cycles_per_bit pad (2)
:sigcomp_version pad (2)
:partial_state_id_length pad (2)
:state_length pad (2)
at (64)
:byte_copy_left pad (2)
:byte_copy_right pad (2)
:remaining_cycles pad (2)
:check_memory pad (1)
:check_memory_lsb pad (1)
:check_cycles pad (1)
:check_cycles_lsb pad (1)
at (127)
:decompression_failure
at (128)
; Set up a 1-byte buffer
LOAD (byte_copy_left, 32)
LOAD (byte_copy_right, 33)
:test_version
; Input a byte containing the version of SigComp being run
INPUT-BYTES (1, check_memory_lsb, decompression_failure)
COMPARE ($sigcomp_version, $check_memory, decompression_failure,
test_state_access, decompression_failure)
:test_state_access
COMPARE ($partial_state_id_length, 0, decompression_failure,
test_length_equals_zero, test_state_length)
:test_length_equals_zero
; No state was accessed so state_length
; should be zero (first message)
COMPARE ($state_length, 0, decompression_failure, end,
decompression_failure)
:test_state_length
; State was accessed so state_length
; should be 960
COMPARE ($state_length, 960, decompression_failure, test_udvm_memory,
decompression_failure)
:test_udvm_memory
; Copy one byte to
; udvm_memory_size + input - 1
; Succeed when input byte is 0x00
; Fail when input byte is 0x01
INPUT-BYTES (1, check_memory_lsb, decompression_failure)
ADD ($check_memory, $udvm_memory_size)
SUBTRACT ($check_memory, 1)
COPY (32, 1, $check_memory)
:test_udvm_cycles
INPUT-BYTES (1, check_cycles_lsb, decompression_failure)
; Work out the total number of cycles available to the UDVM
; total_UDVM_cycles = cycles_per_bit * (8 * message_size + 1000)
;
; = cycles_per_bit * (8 * (partial_state_id_length + 3) + 1000)
LOAD (remaining_cycles, $partial_state_id_length)
ADD ($remaining_cycles, 3)
MULTIPLY ($remaining_cycles, 8)
ADD ($remaining_cycles, 1000)
MULTIPLY ($remaining_cycles, $cycles_per_bit)
ADD ($remaining_cycles, $check_cycles)
set (cycles_used_by_bytecode, 856)
SUBTRACT ($remaining_cycles, cycles_used_by_bytecode)
COPY (32, $remaining_cycles, 32)
; Copy to use up all cycles available + input byte
; Succeeds when input byte = 0x00
; Fail when input byte = 0x01
:end
; Create 960 bytes of state for future
; reference
END-MESSAGE (0, 0, 960, 64, 128, 6, 0)
The bytecode must be executed a total of four times in order to fully
test the SigComp Useful Values. In the first case, the bytecode is
uploaded as part of the SigComp message with a 1-byte compressed
message corresponding to the version of SigComp being run. This
causes the UDVM to request creation of a new state item and uses a
total of 968 UDVM cycles.
Subsequent tests access this state by uploading the state identifier
as part of the SigComp message. Note that the SigComp message should
not contain a returned feedback item (as this would cause the
bytecode to calculate the total number of available UDVM cycles
incorrectly).
A 3-byte compressed message is required for the second and subsequent
cases, the first byte of which is the version of SigComp in use,
0xnn. If the message is 0xnn0000, then the UDVM should successfully
terminate using exactly the number of available UDVM cycles.
However, if the message is 0xnn0001, then the UDVM should use too
many cycles and hence terminate with decompression failure.
Furthermore, if the message is 0xnn0100, then decompression failure
must occur because the UDVM attempts to write beyond its available
memory.
3.2. Cycles Checking
As discussed in Section 3.1, it is possible to write an
implementation that takes a liberal approach to checking the cycles
used and allows some extra cycles. The implementer must be sure that
decompression failure does not occur too early and that in the case
of excessive use of cycles, decompression failure does eventually
occur. This test checks that:
1. Decompression failure occurs eventually when there is an infinite
loop.
at (64)
:byte_copy_left pad (2)
:byte_copy_right pad (2)
:value pad (2)
:copy_next pad (2)
at(128)
MULTILOAD (byte_copy_left, 4, 32, 41, 0, 34)
; Set up a 10-byte buffer
; Set the value to copy
; Copy it 100 times,
; output the value,
; increment the counter
:loop
COPY (value, 2, $byte_copy_left)
COPY-OFFSET (2, 100, $copy_next)
OUTPUT (value, 2)
ADD ($value, 1)
JUMP (loop)
If the cycles are counted exactly and cycles per bit (cpb) = 16, then
decompression failure will occur at COPY-OFFSET when value = 180 =
0xB4. If cpb = 32, then decompression failure will occur when value
= 361 = 0x0169. If they are not counted exactly, then decompression
failure MUST occur eventually.
3.3. Message-based Transport
This section provides a set of messages to test the SigComp header
over a message-based transport such as UDP. The messages test that
the following boundary cases have been correctly implemented:
1. The UDVM bytecode is copied to different areas of the UDVM
memory.
2. The decompression memory size is set to an incorrect value.
3. The SigComp message is too short.
4. The destination address is invalid.
The basic version of the code used in the test is given below. Note
that the code is designed to calculate the decompression memory size
based on the Useful Values provided to the UDVM:
:udvm_memory_size pad (2)
:cycles_per_bit pad (2)
:sigcomp_version pad (2)
:partial_state_id_length pad (2)
:state_length pad (2)
at (128)
:code_start
; udvm_memory_size for message-based transport
; = DMS - total_message_size
ADD ($udvm_memory_size, total_message_size)
OUTPUT (udvm_memory_size, 2)
END-MESSAGE (0, 0, 0, 0, 0, 0, 1)
:code_end
set (header_size, 3)
set (code_size, (code_end - code_start))
set (total_message_size, (header_size + code_size))
A number of complete SigComp messages are given below, each
containing some or all of the above code. In each case, it is
indicated whether the message will successfully output the
decompression memory size or whether it will cause a decompression
failure to occur (together with the reason for the failure):
SigComp message: Effect:
0xf8 Fails (message too short)
0xf800 Fails (message too short)
0xf800 e106 0011 2200 0223 Outputs the decompression_memory_size
0x0000 0000 0000 01
0xf800 f106 0011 2200 0223 Fails (message too short)
0x0000 0000 0000 01
0xf800 e006 0011 2200 0223 Fails (invalid destination address)
0x0000 0000 0000 01
0xf800 ee06 0011 2200 0223 Outputs the decompression_memory_size
0x0000 0000 0000 01
The messages should be decompressed in the order given to check that
an error in one message does not interfere with the successful
decompression of subsequent messages.
The two messages that successfully decompress each use a total of 5
UDVM cycles.
3.4. Stream-based Transport
This section provides a byte stream to test the SigComp header and
delimiters over a stream-based transport such as TCP. The byte
stream tests all of the boundary cases covered in Section 3.2, as
well as the following cases specific to stream-based transports:
1. Quoted bytes are used by the record marking scheme.
2. Multiple delimiters are used between the same pair of messages.
3. Unnecessary delimiters are included at the start of the stream.
The basic version of the code used in the test is given below. Note
that the code is designed to calculate the decompression memory size
based on the Useful Values provided to the UDVM:
:udvm_memory_size pad (2)
:cycles_per_bit pad (2)
:sigcomp_version pad (2)
:partial_state_id_length pad (2)
:state_length pad (2)
at (128)
; udvm_memory_size for stream based transport = DMS / 2
MULTIPLY ($udvm_memory_size, 2)
OUTPUT (udvm_memory_size, 2)
OUTPUT (test_record_marking, 5)
END-MESSAGE (0, 0, 0, 0, 0, 0, 0)
:test_record_marking
byte (255, 255, 255, 255, 255)
The above assembly code has been compiled and used to generate the
following byte stream:
0xffff f801 7108 0002 2200 0222 a092 0523 0000 0000 0000 00ff 00ff
0x03ff ffff ffff ffff f801 7e08 0002 2200 0222 a3d2 0523 0000 0000
0x0000 00ff 04ff ffff ffff ffff ffff ff
Note that this byte stream can be divided into five distinct portions
(two SigComp messages and three sets of delimiters) as illustrated
below:
Portion of byte stream: Meaning:
0xffff Delimiter
0xf801 7108 0002 2200 0222 a092 0523 First message
0x0000 0000 0000 00ff 00ff 03ff ffff
0xffff ffff Delimiter
0xf801 7e08 0002 2200 0222 a3d2 0523 Second message
0x0000 0000 0000 00ff 04ff ffff ff
0xffff ffff ffff Delimiter
When the complete byte stream is supplied to the decompressor
dispatcher, the record marking scheme must use the delimiters to
partition the stream into two distinct SigComp messages. Both of
these messages successfully output the decompression memory size (as
a 2-byte value), followed by 5 consecutive 0xff bytes to test that
the record marking scheme is working correctly. A total of 11 UDVM
cycles are used in each case.
It must also be checked that the dispatcher can handle the same error
cases as covered in Section 3.2. Each of the following byte streams
should cause a decompression failure to occur for the reason stated:
Byte stream: Reason for failure:
0xf8ff ff Message too short
0xf800 ffff Message too short
0xf801 8108 0002 2200 0222 a092 0523 ffff Message too short
0x0000 0000 0000 00ff 00ff 03ff ffff
0xf801 7008 0002 2200 0222 a092 0523 ffff Invalid destination
0x0000 0000 0000 00ff 04ff ffff ff
3.5. Input Past the End of a Message
This section gives assembly code to test that the implementation
correctly handles input past the end of a SigComp message. The code
is designed to test that the following boundary cases have been
correctly implemented:
1. An INPUT instruction requests data that lies beyond the end of
the message. In this case, the dispatcher should not return any
data to the UDVM. Moreover, the message bytes held by the
dispatcher should still be available for retrieval by subsequent
INPUT instructions.
2. The INPUT-BYTES instruction is used after part of a byte has been
input (e.g., by the INPUT-BITS instruction). In this case, the
remaining partial byte must be discarded, even if the INPUT-BYTES
instruction requests data that lies beyond the end of the
message.
at (64)
:byte_copy_left pad (2)
:byte_copy_right pad (2)
:input_bit_order pad (2)
:result pad (1)
:result_lsb pad (6)
:right
at (128)
LOAD (byte_copy_left, result)
LOAD (byte_copy_right, right)
:start
; Input bits to ensure that the remaining message is not byte aligned
INPUT-BITS (9, result, decompression_failure1) ; Input 0x1FF (9 bits)
; Attempt to read 7 bytes
INPUT-BYTES (7, result, next_bytes) ; This should fail, throw away
; 7 bits with value Ox7a and
; jump to next_bytes
:decompression_failure1
DECOMPRESSION-FAILURE ; This instruction is never
; executed but is used to
; separate success and failure
; to input bytes.
:next_bytes
; Read 7 bits - this removes the byte alignment of the message
; If the bits have not been thrown away where they should be, then
; the message will be 1 byte longer than necessary and the output
; will be incorrect.
INPUT-BITS (7, result, decompression_failure1) ; Input 0x00 (7 bits)
; Read 2 bytes
INPUT-BYTES (2, result, decompression_failure1)
; Throw away 1 bit value 0
; Input 0x6869
OUTPUT (result, 2) ; Output 0x6869
; Attempt to read more bits than
INPUT-BITS (16, result, bits) ; there are to ensure they
; remain available
:decompression_failure2
DECOMPRESSION-FAILURE ; This instruction is never
; executed but is used to
; separate success and failure
; to input bits.
:bits
; Read 8 bits
INPUT-BITS (8, result, decompression_failure2) ; Input 0x21 or fail
OUTPUT (result_lsb, 1) ; Output 0x21
:end_message
END-MESSAGE (0, 0, 0, 0, 0, 0, 0)
If the compressed message is 0xfffa 0068 6921, then the code
terminates successfully with the output 0x6869 21, and a total of 23
UDVM cycles are used. However, if the compressed message is 0xfffa
0068 69, then decompression failure occurs (at the final INPUT-BITS).
4. Torture Tests for State Handler
The following sections give code to test the various functions of the
SigComp state handler.
4.1. SigComp Feedback Mechanism
This section gives assembly code to test the SigComp feedback
mechanism. The code is designed to test that the following boundary
cases have been correctly implemented:
1. Both the short and the long versions of the SigComp feedback item
are used.
2. The chain of returned SigComp parameters is terminated by a non-
zero value.
at (64)
:type pad (1)
:type_lsb pad (1)
:requested_feedback_location pad (1)
:requested_feedback_length pad (1)
:requested_feedback_bytes pad (127)
:returned_parameters_location pad (2)
:length_of_partial_state_id_a pad (1)
:partial_state_identifier_a pad (6)
:length_of_partial_state_id_b pad (1)
:partial_state_identifier_b pad (12)
:length_of_partial_state_id_c pad (1)
:partial_state_identifier_c pad (20)
:terminate_returned_parameters pad (1)
align (128)
set (q_bit, 1)
set (s_bit, 0)
set (i_bit, 0)
set (flags, (((4 * q_bit) + (2 * s_bit)) + i_bit))
INPUT-BYTES (1, type_lsb, decompression_failure)
COMPARE ($type, 1, short_feedback_item, long_feedback_item,
decompression_failure)
:short_feedback_item
set (requested_feedback_data, 127)
set (short_feedback_value, ((flags * 256) + requested_feedback_data))
LOAD (requested_feedback_location, short_feedback_value)
JUMP (return_sigcomp_parameters)
:long_feedback_item
set (requested_feedback_field, 255)
set (long_feedback_value, ((flags * 256) + requested_feedback_field))
LOAD (requested_feedback_location, long_feedback_value)
MEMSET (requested_feedback_bytes, 127, 1, 1)
:return_sigcomp_parameters
set (cpb, 0)
set (dms, 1)
set (sms, 0)
set (sigcomp_version, 1)
set (parameters_msb, (((64 * cpb) + (8 * dms)) + sms))
set (sigcomp_parameters, ((256 * parameters_msb) + sigcomp_version))
LOAD (returned_parameters_location, sigcomp_parameters)
LOAD (length_of_partial_state_id_a, 1536) ; length 6 first byte 0
LOAD (length_of_partial_state_id_b, 3072) ; length 12 first byte 0
LOAD (length_of_partial_state_id_c, 5120) ; length 20 first byte 0
LOAD (terminate_returned_parameters, 5376) ; length 21
; used to terminate the
; returned parameters
MEMSET (partial_state_identifier_a, 6, 0, 1)
MEMSET (partial_state_identifier_b, 12, 0, 1)
MEMSET (partial_state_identifier_c, 20, 0, 1)
END-MESSAGE (requested_feedback_location,
returned_parameters_location, 0, 0, 0, 0, 0)
:decompression_failure
DECOMPRESSION-FAILURE
When the above code is executed, it supplies a requested feedback
item to the state handler. If the compressed message is 0x00, then
the short (1-byte) version of the feedback is used. Executing the
bytecode in this case costs a total of 52 UDVM cycles. Assuming that
the feedback request is successful, the feedback item should be
returned in the first SigComp message to be sent in the reverse
direction. The SigComp message returning the feedback should begin
as follows:
+---+---+---+---+---+---+---+---+
| 1 1 1 1 1 1 | X | first header byte
+---+---+---+---+---+---+---+---+
| 0 | 127 | returned feedback field
+---+---+---+---+---+---+---+---+
So the first 2 bytes of the returning SigComp message should be
0xfn7f where n = c, d, e, or f (the choice of n is determined by the
compressor generating the returning SigComp message, which is not
under the control of the above code).
If the compressed message is 0x01, then the long version of the
feedback item is used. Executing the bytecode in this case costs a
total of 179 UDVM cycles and the SigComp message returning the
feedback should begin as follows:
+---+---+---+---+---+---+---+---+
| 1 1 1 1 1 1 | X | first header byte
+---+---+---+---+---+---+---+---+
| 1 | 127 | returned feedback length
+---+---+---+---+---+---+---+---+
| 1 | ^
+---+---+---+---+---+---+---+---+ |
| 2 | |
+---+---+---+---+---+---+---+---+
| 3 | returned feedback field
+---+---+---+---+---+---+---+---+
So the first 129 bytes of the SigComp message should be 0xfnff 0102
0304 ... 7e7f where n = c, d, e, or f as above.
As well as testing the requested and returned feedback items, the
above code also announces values for each of the SigComp parameters.
The supplied version of the code announces only the minimum possible
values for the cycles_per_bit, decompression_memory_size,
state_memory_size, and SigComp_version (although this can easily be
adjusted to test different values for these parameters).
The code should also announce the availability of state items with
the following partial state identifiers:
0x0001 0203 0405
0x0001 0203 0405 0607 0809 0a0b
0x0001 0203 0405 0607 0809 0a0b 0c0d 0e0f 1011 1213
Note that different implementations may make use of the announcement
information in different ways. It is a valid implementation choice
to simply ignore all of the announcement data and use only the
minimum resources that are guaranteed to be available to all
endpoints. However, the above code is useful for checking that an
endpoint interprets the announcement data correctly (in particular
ensuring that it does not mistakenly use resources that have not in
fact been announced).
4.2. State Memory Management
The following section gives assembly code to test the memory
management features of the state handler. The code checks that the
correct states are retained by the state handler when insufficient
memory is available to store all of the requested states.
The code is designed to test that the following boundary cases have
been correctly implemented:
1. A state item is created that exceeds the total state_memory_size
for the compartment.
2. States are created with a non-zero state_retention_priority.
3. A new state item is created that has a lower
state_retention_priority than existing state items in the
compartment.
For the duration of this test, it is assumed that all states will be
saved in a single compartment with a state_memory_size of 2048 bytes.
at (64)
:byte_copy_left pad (2)
:byte_copy_right pad (2)
:order pad (2)
:type pad (1)
:type_lsb pad (1)
:state_length pad (2)
:state_retention_priority pad (2)
at(127)
:decompression_failure
at (128)
MULTILOAD (byte_copy_left, 2, state_start, order_data)
INPUT-BYTES (1, type_lsb, decompression_failure)
COMPARE ($type, 5, general_test, large_state, verify_state)
:general_test
COMPARE ($type, 3, start, state_present, state_not_present)
:start
MULTIPLY ($type, 6)
ADD ($type, order_data)
LOAD (order, $type)
ADD ($type, 6)
; Finish with the value (order_data + 6*n) in order where
; n is the input value 0x00, 0x01, or 0x02
; type = order + 6
; These values are used to index into the 'order_data'
; that is used to work out state retention priorities and lengths
:loop
COPY ($order, 2, state_retention_priority)
COMPARE ($order, $type, continue, end, decompression_failure)
:continue
; Set up a state creation each time through the loop
LOAD (state_length, $state_retention_priority)
MULTIPLY ($state_length, 256)
STATE-CREATE ($state_length, state_start, 0, 6,
$state_retention_priority)
ADD ($order, 2)
JUMP (loop)
:state_present
; Access the states that should be present
STATE-ACCESS (state_identifier_a, 6, 0, 0, 0, 0)
STATE-ACCESS (state_identifier_b, 6, 0, 0, 0, 0)
STATE-ACCESS (state_identifier_c, 6, 0, 0, 0, 0)
STATE-ACCESS (state_identifier_e, 6, 0, 0, 0, 0)
JUMP (end)
:state_not_present
; Check that the state that shouldn't be present is not present.
STATE-ACCESS (state_identifier_d, 6, 0, 0, 0, 0)
JUMP (end)
:large_state
STATE-CREATE (2048, state_start, 0, 6, 0)
JUMP (end)
:verify_state
STATE-ACCESS (large_state_identifier, 6, 0, 0, 0, 0)
JUMP (end)
:end
END-MESSAGE (0, 0, 0, 0, 0, 0, 0)
at (512)
:state_start
byte (116, 101, 115, 116)
:order_data
; This data is used to generate the retention priority
; and state length of each state creation.
word (0, 1, 2, 3, 4, 3, 2, 1, 0)
:state_identifier_a
byte (142, 234, 75, 67, 167, 135)
:state_identifier_b
byte (249, 1, 14, 239, 86, 123)
:state_identifier_c
byte (35, 154, 52, 107, 21, 166)
:state_identifier_d
byte (180, 15, 192, 228, 77, 44)
:state_identifier_e
byte (212, 162, 33, 71, 230, 10)
:large_state_identifier
byte (239, 242, 188, 15, 182, 175)
The above code must be executed a total of 7 times in order to
complete the test. Each time the code is executed, a 1-byte
compressed message should be provided as below. The effects of the
messages are given below. States are described in the form (name, x,
y) where name corresponds to the name of the identifier in the
mnemonic code, x is the length of the state, and y is the retention
priority of the state.
Message: Effect: #cycles:
0x00 create states: 811
(a,0,0),
(b,256,1),
(c,512,2)
0x01 create states: 2603
(d,768,3),
(e,1024,4) - deleting a, b, c
0x02 create states: 811
(c,512,2), - deleting d
(b,256,1),
(a,0,0)
0x03 access states a,b,c,e 1805
0x04 access state d - not present so decompression failure
0x05 create states: 2057
(large, 2048,0) - deleting a, b, c, e
0x06 access large state 1993
Note that as new states are created, some of the existing states will
be pushed out of the compartment due to lack of memory.
4.3. Multiple Compartments
This section gives assembly code to test the interaction between
multiple SigComp compartments. The code is designed to test that the
following boundary cases have been correctly implemented:
1. The same state item is saved in more than one compartment.
2. A state item stored in multiple compartments has the same state
identifier but a different state_retention_priority in each case.
3. A state item is deleted from one compartment but still belongs to
a different compartment.
4. A state item belonging to multiple compartments is deleted from
every compartment to which it belongs.
The test requires a total of three compartments to be available,
which will be referred to as Compartment 0, Compartment 1, and
Compartment 2. Each of the three compartments should have a
state_memory_size of 2048 bytes.
The assembly code for the test is given below:
at (64)
:byte_copy_left pad (2)
:byte_copy_right pad (2)
:type pad (1)
:type_lsb pad (1)
at (127)
:decompression_failure
at (128)
MULTILOAD (byte_copy_left, 2, state_start, state_end)
INPUT-BYTES (1, type_lsb, decompression_failure)
COMPARE ($type, 3, create_state, overwrite_state, temp)
:temp
COMPARE ($type, 5, overwrite_state, access_state, error_conditions)
:create_state
; starting byte identified by $type according to input:
; Input 0x00 0x01 0x02
; $type 512 513 514
ADD ($type, state_start)
STATE-CREATE (448, $type, 0, 6, 0)
; create state again, beginning in different place in buffer
; starting byte identified by $type according to input:
; Input 0x00 0x01 0x02
; $type 515 516 517
ADD ($type, 3)
STATE-CREATE (448, $type, 0, 6, 0)
; create a third time beginning in different place again
; starting byte identified by $type according to input:
; Input 0x00 0x01 0x02
; $type 516 517 515
SUBTRACT ($type, temp_one)
REMAINDER ($type, 3)
ADD ($type, temp_two)
STATE-CREATE (448, $type, 0, 6, 0)
:common_state
STATE-CREATE (448, temp_three, 0, 6, $type)
JUMP (end)
:overwrite_state
STATE-CREATE (1984, 32, 0, 6, 0)
JUMP (end)
:access_state
STATE-ACCESS (state_identifier_c, 6, 0, 0, 0, 0)
STATE-ACCESS (state_identifier_d, 6, 0, 0, 0, 0)
STATE-ACCESS (state_identifier_f, 6, 0, 0, 0, 0)
STATE-ACCESS (state_identifier_g, 6, 0, 0, 0, 0)
:end
END-MESSAGE (0, 0, 0, 0, 0, 0, 0)
:error_conditions
COMPARE ($type, 7, access_a, access_b, access_e)
:access_a
STATE-ACCESS (state_identifier_a, 6, 0, 0, 0, 0)
JUMP (end)
:access_b
STATE-ACCESS (state_identifier_b, 6, 0, 0, 0, 0)
JUMP (end)
:access_e
STATE-ACCESS (state_identifier_e, 6, 0, 0, 0, 0)
JUMP (end)
at (512)
:state_start
byte (0, 1, 2, 3, 4, 5, 6)
:state_end
set (temp_one, (state_start + 2)) ; = 514
set (temp_two, (state_start + 3)) ; = 515
set (temp_three, (state_end - 1)) ; = 518
:state_identifier_a ; start state at 512
byte (172, 166, 11, 142, 178, 131)
:state_identifier_b ; start state at 513
byte (157, 191, 175, 198, 61, 210)
:state_identifier_c ; start state at 514
byte (52, 197, 217, 29, 83, 97)
:state_identifier_d ; start state at 515
byte (189, 214, 186, 42, 198, 90)
:state_identifier_e ; start state at 516
byte (71, 194, 24, 20, 238, 7)
:state_identifier_f ; start state at 517
byte (194, 117, 148, 29, 215, 161)
:state_identifier_g ; start state at 518
byte (72, 135, 156, 141, 233, 14)
The above code must be executed a total of 9 times in order to
complete the test. Each time the code is executed, a 1-byte
compressed message N should be provided, taking the values 0x00 to
0x08 in ascending order (so the compressed message should be 0x00 the
first time the code is run, 0x01 the second, and so on).
If the code makes a state creation request, then the state must be
saved in Compartment (N modulo 3).
When the compressed message is 0x00, 0x01, or 0x02, the code makes
four state creation requests in compartments 0, 1, and 2,
respectively. This creates a total of seven distinct state items
referred to as State a through State g. The states should be
distributed among the three compartments as illustrated in Figure 1
(note that some states belong to more than one compartment).
When the compressed message is 0x03 or 0x04, the code overwrites all
of the states in Compartments 0 and 1, respectively. This means that
States a, b, and e will be unavailable because they are no longer
present in any of the three compartments.
When the compressed message is 0x05, the code checks that the States
c, d, f, and g are still available. Decompression should terminate
successfully in this case.
When the compressed message is 0x06, 0x07, or 0x08, the code attempts
to access States a, b, and e, respectively. Decompression failure
should occur in this case because the relevant states are no longer
available.
The cost in UDVM cycles for each compressed message is given below
(except for messages 0x06, 0x07, and 0x08 where decompression failure
should to occur):
Compressed message: 0x00 0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08
Cost in UDVM cycles: 1809 1809 1809 1993 1994 1804 N/A N/A N/A
+-----------------------------+
| Compartment 0 |
| |
| |
| State a |
| |
| +-------------------+---------+
| | | |
| | | |
| | State d | |
| | | |
| | | |
+---------+---------+---------+ | |
| | | | | |
| | | | | |
| | State e | State g | | State c |
| | | | | |
| | | | | |
| +---------+---------+---------+ |
| | | |
| | | |
| State b | State f | |
| | | |
| | | Compartment 2 |
| +---------+-------------------+
| |
| |
| |
| |
| Compartment 1 |
+-----------------------------+
Figure 1: States created in the three compartments
4.4. Accessing RFC 3485 State
This section gives assembly code to test accessing SIP-SDP static
dictionary state [3]. The code first accesses the state and then
outputs the result.
at (32)
:input pad (1)
:input2 pad (1)
:input3 pad (1)
at (128)
STATE-ACCESS (sip_dictionary, 20, 0xcfe, 1, input, 0)
STATE-ACCESS (sip_dictionary, 6, 0xcff, 1, input2, 0)
STATE-ACCESS (sip_dictionary, 12, 0xd00, 1, input3, 0)
OUTPUT (input, 3)
END-MESSAGE (0, 0, 0, 0, 0, 0, 0)
:sip_dictionary
byte (0xfb, 0xe5, 0x07, 0xdf, 0xe5, 0xe6)
byte (0xaa, 0x5a, 0xf2, 0xab, 0xb9, 0x14)
byte (0xce, 0xaa, 0x05, 0xf9, 0x9c, 0xe6)
byte (0x1b, 0xa5)
The output of the code is 0x5349 50, and the cost is 11 UDVM cycles.
4.5. Bytecode State Creation
This section gives assembly code to test storing bytecode using
END-MESSAGE and later loading the bytecode using a partial state
identifier within the SigComp header. The assembly code is designed
to test the following cases:
1. The bytes to be saved are changed after the state create request
has been made.
2. The uploaded bytecode is modified before execution.
3. The bytecode is loaded using the partial state identifier and is
modified before execution.
4. The bytecode is loaded to an address lower than 128, using the
partial state identifier.
5. The bytecode is loaded using the partial state identifier. Part
of the loaded memory is reserved area, which is overwritten after
loading the bytecode.
6. The loading of the bytecode fails because the partial state
identifier is too short.
at (30)
:save_area1
set (saved_instr1, (save_area1 + (code_start2 - start_saved))) ; = 33
at (80)
:save_area2
set (saved_instr2, (save_area2 + (code_start2 - start_saved))) ; = 83
at (128)
:code_start
COPY (start_saved, saved_len, save_area1)
; copy 'ok2', OUTPUT (save_area2,3) END-MESSAGE
; to position 30 and create as state
STATE-CREATE (saved_len, save_area1, saved_instr1, 6, 10)
set (modify1, (save_area1 + 5)) ; = 35
LOAD (modify1, 0x1e03)
; modify save_area2 to be save_area1 in the
; created state
COPY (start_saved, saved_len, save_area2)
STATE-CREATE (saved_len, save_area2, saved_instr2, 20, 10)
STATE-CREATE (saved_len, save_area2, saved_instr2, 12, 10)
; copy 'ok2', OUTPUT (save_area2,3) END-MESSAGE
; to position 80 and create as state twice with
; min access len 20 and 12
JUMP (modify)
:ok1
byte (0x4f, 0x4b, 0x31)
set (after_output_minus1, (after_output - 1))
:modify
INPUT-BYTES (1, after_output_minus1, decompression_failure)
; Input overwrites the next instruction
OUTPUT (ok1, 3) ; Now is OUTPUT (ok1, 2) so output is 0x4f4b
:after_output
; Save from ok1 to the opcode of END-MESSAGE
set (modify_len, ((after_output + 1) - ok1)) ; = 13
END-MESSAGE (0, 0, modify_len, ok1, modify, 6, 10)
; Save 'ok1', INPUT-BYTES, OUTPUT as state
set (saved_len, (end_saved - start_saved)) ; = 8
:start_saved
byte (0x4f, 0x4b, 0x32)
:code_start2
; Translated bytecode for OUTPUT (save_area2, 3)
byte (0x22, 0xa0, 0x50, 0x03)
; Translated bytecode for END-MESSAGE (0, 0, 0, 0, 0, 0, 0)
; The zeros do not need to be sent because UDVM is initialised to 0
byte (0x23)
:end_saved
:decompression_failure
The outputs and cycle usages are:
Message Output Cycles
1 0x4f4b 66
2 0x4f4b 31 7
3 0x4f4b 32 5
4 0x0000 32 5
5 None Decompression failure
First message: mnemonic code annotated above
0xf804 6112 a0be 081e 2008 1e21 060a 0e23 be03 12a0 be08 a050 2008
0xa050 a053 140a 2008 a050 a053 0c0a 1606 004f 4b31 1c01 a0b3 fc22
0xa0a8 0323 0000 0da0 a8a0 ab06 0a4f 4b32 22a0 5003 2302
Second message: access and run last state saved by previous message -
'ok1', INPUT-BYTES, OUTPUT, END-MESSAGE.
0xf905 b88c e72c 9103
Third message: access and run state from save_area2 with 12 bytes of
state identifier - 'ok2', INPUT-BYTES, OUTPUT, END-MESSAGE.
0xfb24 63cd ff5c f8c7 6df6 a289 ff
Fourth message: access and run state from save_area1. The state is
'ok2', INPUT-BYTES, OUTPUT, END-MESSAGE but the first two bytes
should be overwritten when initialising UDVM memory.
0xf95b 4b43 d567 83
Fifth message: attempt to access state from save_area2 with fewer
than 20 bytes of state identifier.
0xf9de 8126 1199 1f
5. Security Considerations
This document describes torture tests for the SigComp protocol RFC
3320 [2]. Consequently, the security considerations for this
document match those of SigComp.
In addition, the torture tests include tests for a significant number
of "boundary and error cases" for execution of the UDVM bytecode.
Boundary and error problems are common vectors for security attacks,
so ensuring that a UDVM implementation executes this set of torture
tests correctly should contribute to the security of the
implementation.
6. Acknowledgements
Thanks to Richard Price and Pekka Pessi for test contributions and to
Pekka Pessi and Cristian Constantin, who served as committed working
group document reviewers.
7. Normative References
[1] Surtees, A. and M. West, "Signaling Compression (SigComp) Users'
Guide", RFC 4464, May 2006.
[2] Price, R., Bormann, C., Christoffersson, J., Hannu, H., Liu, Z.,
and J. Rosenberg, "Signaling Compression (SigComp)", RFC 3320,
January 2003.
[3] Garcia-Martin, M., Bormann, C., Ott, J., Price, R., and A.B.
Roach, "The Session Initiation Protocol (SIP) and Session
Description Protocol (SDP) Static Dictionary for Signaling
Compression (SigComp)", RFC 3485, February 2003.
[4] Roach, A.B., "A Negative Acknowledgement Mechanism for Signaling
Compression", RFC 4077, May 2005.
Appendix A. UDVM Bytecode for the Torture Tests
The following sections list the raw UDVM bytecode generated for each
test. The bytecode is presented in the form of a complete SigComp
message, including the appropriate header. It is followed by input
messages, the output they produce, and where the decompression
succeeds the number of cycles used.
In some cases, the test is designed to be run several times with
different compressed messages appended to the code. In the cases
where multiple whole messages are used for a test, e.g.,
Appendix A.2.3, these are supplied. In the case where decompression
failure occurs, the high-level reason for it is given as a reason
code defined in NACK [4].
Note that the different assemblers can output different bytecode for
the same piece of assembly code, so a valid assembler can produce
results different from those presented below. However, the following
bytecode should always generate the same results on any UDVM.
A.1. Instructions
A.1.1. Bit Manipulation
0xf80a 7116 a07f 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x01c0 00ff 8055 5502 202a 0321 0420 0305 21ff 2286 0401 20c0 ff02
0x2060 0320 0421 6005 2061 2286 0423
Input: None
Output: 0x0150 0000 febf 0000
Cycles: 22
A.1.2. Arithmetic
0xf80a a11c 01a0 450b 0722 0116 a077 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x06c0 00ff 9941 0720 0108 20a3 e909 20a0 650a 200b 2286 0406 21c0
0xff07 2162 0821 6109 2061 0a21 6222 8604 23
Input: 0x00
Output: 0x0000 0000 0000 0004
Cycles: 25
Input: 0x01
DECOMPRESSION-FAILURE DIV_BY_ZERO
Input: 0x02
DECOMPRESSION-FAILURE DIV_BY_ZERO
A.1.3. Sorting
0xf80d c10c 8802 170b 8802 1722 a12e 2d23 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0a00 0a00 1100 0700 1600 0300 0300 0300 1300 0100 1000 0e00
0x0800 0200 0d00 1400 1200 1700 0f00 1500 0c00 0600 096e 6720 6975
0x6920 7469 742c 2079 6f75 2720 5346 6f6e 6761 2075 7272 646f 2074
0x6f6e 2e2e 0070 6570 206e 7472 656e 69
Input: None
Output: 0x466f 7264 2c20 796f 7527 7265 2074 7572 6e69 6e67
0x2069 6e74 6f20 6120 7065 6e67 7569 6e2e 2053 746f
0x7020 6974 2e
Cycles: 371
A.1.4. SHA-1
0xf808 710d a0c3 03a0 4422 a044 140d a0c6 38a0 4422 a044 140e 86a0
0xfe0e a042 a0ff 0da0 fe8e a044 22a0 4414 0e86 a0ff 0ea0 42a1 070d
0xa0ff a280 a0ff 22a0 ff14 2300 0000 0000 0000 6162 6361 6263 6462
0x6364 6563 6465 6664 6566 6765 6667 6866 6768 6967 6869 6a68 696a
0x6b69 6a6b 6c6a 6b6c 6d6b 6c6d 6e6c 6d6e 6f6d 6e6f 706e 6f70 7161
0x3031 3233 3435 3637
Input: None
Output: 0xa999 3e36 4706 816a ba3e 2571 7850 c26c 9cd0 d89d
0x8498 3e44 1c3b d26e baae 4aa1 f951 29e5 e546 70f1
0x12ff 347b 4f27 d69e 1f32 8e6f 4b55 73e3 666e 122f
0x4f46 0452 ebb5 6393 4f46 0452 ebb5 6393 4f46 0452
Cycles: 17176
A.1.5. LOAD and MULTILOAD
0xf803 610e 87a0 840e a082 c080 0ec0 80a0 860e c084 c084 2287 081c
0x01a0 4127 0820 0206 203c 0f60 03a0 a2a0 b187 0f60 042a 87c0 80c0
0x8422 8708 23
Input: 0x00
Output: 0x0084 0084 0086 0086 002a 0080 002a 002a
Cycles: 36
Input: 0x01
DECOMPRESSION-FAILURE MULTILOAD_OVERWRITTEN
Input: 0x02
DECOMPRESSION-FAILURE MULTILOAD_OVERWRITTEN
A.1.6. COPY
0xf803 910e 208e 0e86 860e a042 8712 2087 210e 8680 4100 1286 a055
0xa041 2220 a077 0e86 200e a042 3015 2004 a041 0112 2004 3022 3004
0x1230 042e 2220 0223
Input: None
Output: 0x4040 4040 4040 4040 4040 4040 4040 4040 4040 4040
0x4040 4040 4040 4040 4040 4040 4141 4141 4141 4141
0x4141 4141 4141 4141 4141 4141 4141 4141 4141 4141
0x4141 4141 4141 4141 4141 4141 4141 4141 4141 4141
0x4141 4141 4141 4141 4141 4141 4141 4141 4141 4141
0x4141 4141 4141 4141 4141 4141 4141 4141 4141 5541
0x4243 4443 44
Cycles: 365
A.1.7. COPY-LITERAL and COPY-OFFSET
0xf806 110e 2080 4100 0e86 860e a042 870e a044 2113 2087 2222 8608
0x0ea0 44a0 9c13 2002 2222 a09c 020e 86a0 480e a042 a052 0ea0 44a0
0x5215 a048 0aa0 4101 1402 0622 0ea0 4606 1463 0422 2261 0a0e a044
0xa050 1404 0422 22a0 4402 1405 0422 22a0 4402 2260 0a23
Input: None
Output: 0x4141 4141 0061 4141 4141 494A 4142 4344 494A 4142
0x004A 004E 4748 4845 4647 4748 4546
Cycles: 216
A.1.8. MEMSET
0xf801 810e 8687 0ea0 42a0 8115 86a0 8100 0115 a081 0f86 0f22 8710
0x23
Input: None
Output: 0x8040 4f5e 6d7c 8b9a a9b8 c7d6 e5f4 0312
Cycles: 166
A.1.9. CRC
0xf801 8115 a046 1801 0115 a05e 1487 011c 02a0 4413 1b62 a046 2c0e
0x23
Input: 0x62cb
Output: None
Cycles: 95
Input: 0xabcd
DECOMPRESSION FAILURE USER_REQUESTED (CRC mismatch)
A.1.10. INPUT-BITS
0xf801 511d 62a0 4614 22a0 4602 0622 010a 2207 0622 0116 ee23
Input: 0x932e ac71
Output: 0x0000 0002 0002 0013 0000 0003 001a 0038
Cycles: 66
A.1.11. INPUT-HUFFMAN
0xf801 d11e a046 1c02 6200 6262 6200 ff00 22a0 4602 0622 010a 2207
0x0622 0116 e623
Input: 0x932e ac71 66d8 6f
Output: 0x0000 0003 0008 04d7 0002 0003 0399 30fe
Cycles: 84
A.1.12. INPUT-BYTES
0xf802 710e 86a0 480e a042 a04c 1d62 a046 1d22 a046 0206 2202 0a22
0x071c 62a0 480e 22a0 4862 0622 0116 e523
Input: 0x932e ac71 66d8 6fb1 592b dc9a 9734 d847 a733 874e
0x1bcb cd51 b5dc 9659 9d6a
Output: 0x0000 932e 0001 b166 d86f b100 1a2b 0003 9a97 34d8
0x0007 0001 3387 4e00 08dc 9651 b5dc 9600 599d 6a
Cycles: 130
A.1.13. Stack Manipulation
0xf814 110e a046 8610 0210 6010 a042 2286 0811 8611 6311 a046 2286
0x0816 2800 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 000e a046 200e a048 a140 0724
0x8818 3400 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0018 6400 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 000e a046 a17f 0ea1 7f1a 0fa1 b003
0x0180 c001 8f19 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0023
Input: None
Output: 0x0003 0002 0001 0042 0042 0000 0001 0001
Cycles: 40
A.1.14. Program Flow
0xf803 f10e a044 040e 86a0 9207 20a0 9022 a043 0116 6006 2101 0e86
0xa084 0720 a0a1 22a0 4301 1761 0660 f106 0722 010e 86a0 8407 20a0
0xb622 a043 011a 0462 0860 9fdc f123
Input: None
Output: 0x0001 0102 0203 0304 0405 0506 0707 0708 0808 0909
Cycles: 131
A.1.15. State Creation
0xf809 411c 01a0 45ff 0422 0b17 628f 0d06 0620 0aa1 0a00 1400 0422
0x0117 628f 0c06 0620 0a88 0014 0004 2201 1762 8f16 0606 1c01 a047
0x9fd2 21a0 4863 12a0 e363 a048 0422 0117 628f 0a06 0621 a0e3 0604
0x2201 1762 8f0e 0606 2300 000a 8800 1400 2300 0000 0000 0000 437a
0xe80a 0fdc 1e6a 87c1 b62a 7676 b973 318c 0ef5 0000 0000 0000 0000
0x00c0 cc3f ee79 bcfc 8fd1 0865 e803 52ee 2977 17df 57
Input: 0x01
Output: None
Cycles: 23
Input: 0x02
Output: None
Cycles: 14
Input: 0x03
Output: None
Cycles: 24
Input: 0x0405
DECOMPRESSION-FAILURE INVALID_STATE_ID_LENGTH
Input: 0x0415
DECOMPRESSION-FAILURE INVALID_STATE_ID_LENGTH
Input: 0x0406
Output: None
Cycles: 23
Input: 0x09
Output: None
Cycles: 34
Input: 0x1e06
Output: None
Cycles: 46
Input: 0x1e07
Output: None
Cycles: 47
Input: 0x1e14
Output: None
Cycles: 60
A.1.16. STATE-ACCESS
Set up bytecode:
0xf819 0123 0000 1089 0014 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0022 a20c
0x0423 0000 0000 0000 0074 6573 74
Input: None
0xf819 411c 01a0 45ff 1762 0106 0d1c 1f89 1400 0000 891f 8914 0c04
0xa046 0022 a046 0416 a146 1762 0306 101b 1f87 1400 0000 0016 a136
0x1f89 1306 04a0 4600 16a1 2b1f 8914 0c05 a046 0016 a120 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0023 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 005d f8bc
0x3e20 93b5 abe1 f170 1342 4ce7 fe05 e069 39
Input: 0x00
Output: 0x7465 7374
Cycles: 26
Input: 0x01
Output: 0x7465 7374
Cycles: 15
Input: 0x02
DECOMPRESSION-FAILURE STATE_NOT_FOUND
Input: 0x03
DECOMPRESSION-FAILURE STATE_NOT_FOUND (len < min_acc_len)
Input: 0x04
DECOMPRESSION-FAILURE STATE_TOO_SHORT
A.2. Dispatcher Tests
A.2.1. Useful Values
0xf805 f10e 8620 0ea0 4221 1c01 a047 f817 4263 f306 f317 4300 ed06
0x0c17 4400 e73f e717 44a3 c0e1 07e1 1c01 a047 9fda 0623 4007 2301
0x1220 0163 1c01 a049 9fca 0ea0 4443 0622 0308 2208 0622 a3e8 0822
0x4106 2264 0722 a358 1220 6220 2300 00a3 c086 8706
Input: 1 byte of SigComp version
Output: None
Cycles: 968
0xf93a db1d 3d20 aa
Input: 1 byte of SigComp version then 0x0000
Output: None
Cycles: cycles_per_bit * 1080
Input: 1 byte of SigComp version then 0x0001
DECOMPRESSION-FAILURE CYCLES_EXHAUSTED
Input: 1 byte of SigComp version then 0x0100
DECOMPRESSION-FAILURE SEGFAULT
A.2.2. Cycles Checking
0xf801 a10f 8604 2029 0022 12a0 4402 6014 02a0 6423 22a0 4402 0622
0x0116 ef
Input: None
DECOMPRESSION-FAILURE CYCLES_EXHAUSTED
A.2.3. Message-based Transport
0xf8
Input: None
DECOMPRESSION-FAILURE MESSAGE_TOO_SHORT
0xf800
Input: None
DECOMPRESSION-FAILURE MESSAGE_TOO_SHORT
0xf800 e106 0011 2200 0223 0000 0000 0000 01
Input: None
Output: decompression_memory_size
Cycles: 5
0xf800 f106 0011 2200 0223 0000 0000 0000 01
Input: None
DECOMPRESSION-FAILURE MESSAGE_TOO_SHORT
0xf800 e006 0011 2200 0223 0000 0000 0000 01
Input: None
DECOMPRESSION-FAILURE INVALID_CODE_LOCATION
0xf800 ee06 0011 2200 0223 0000 0000 0000 01
Input: None
Output: decompression_memory_size
Cycles: 5
A.2.4. Stream-based Transport
0xffff f801 7108 0002 2200 0222 a092 0523 0000 0000 0000 00ff 00ff
0x03ff ffff ffff ffff f801 7e08 0002 2200 0222 a3d2 0523 0000 0000
0x0000 00ff 04ff ffff ffff ffff ffff ff
The above stream contains two messages:
Output: decompression_memory_size
Cycles: 11
Output: decompression_memory_size
Cycles: 11
0xf8ff ff
Input: None
DECOMPRESSION-FAILURE MESSAGE_TOO_SHORT
0xf800 ffff
Input: None
DECOMPRESSION-FAILURE MESSAGE_TOO_SHORT
0xf801 8108 0002 2200 0222 a092 0523 ffff 0000 0000 0000 00ff 00ff
0x03ff ffff
Input: None
DECOMPRESSION-FAILURE MESSAGE_TOO_SHORT
0xf801 7008 0002 2200 0222 a092 0523 ffff 0000 0000 0000 00ff 04ff
0xffff ff
Input: None
DECOMPRESSION-FAILURE INVALID_CODE_LOCATION
A.2.5. Input Past the End of a Message
0xf803 210e 86a0 460e a042 a04d 1d09 a046 0a1c 07a0 4606 001d 07a0
0x46ff 1c02 a046 fa22 a046 021d 10a0 4606 001d 08a0 46ff 22a0 4701
0x23
Input: 0xfffa 0068 6921
Output: 0x6869 21
Cycles: 23
Input: 0xfffa 0068 69
DECOMPRESSION-FAILURE USER_REQUESTED (not enough bits)
A.3. State Handler Tests
A.3.1. SigComp Feedback Mechanism
0xf805 031c 01a0 41a0 5517 6001 070e a04f 0ea0 42a4 7f16 0e0e a042
0xa4ff 15a0 44a0 7f01 010e a0c3 a801 0ea0 c5a6 000e a0cc ac00 0ea0
0xd9b4 000e a0ee b500 15a0 c606 0001 15a0 cd0c 0001 15a0 da14 0001
0x23a0 42a0 c3
Input: 0x00
Output: None
Cycles: 52
Input: 0x01
Output: None
Cycles: 179
A.3.2. State Memory Management
0xf81b a10f 8602 89a2 041c 01a0 47f9 1763 0508 a068 a070 1763 0307
0x34a0 5608 2306 0623 a204 0ea0 4463 0623 0612 6202 a04a 1762 6308
0xa058 9fd2 0ea0 4865 0824 8820 6489 0006 6506 2202 16e3 1fa2 1606
0x0000 0000 1fa2 1c06 0000 0000 1fa2 2206 0000 0000 1fa2 2e06 0000
0x0000 161e 1fa2 2806 0000 0000 1614 208b 8900 0600 160c 1fa2 3406
0x0000 0000 1602 2300 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0074 6573
0x7400 0000 0100 0200 0300 0400 0300 0200 0100 008e ea4b 43a7 87f9
0x010e ef56 7b23 9a34 6b15 a6b4 0fc0 e44d 2cd4 a221 47e6 0aef f2bc
0x0fb6 af
Input: 0x00
Output: None
Cycles: 811
Input: 0x01
Output: None
Cycles: 2603
Input: 0x02
Output: None
Cycles: 811
Input: 0x03
Output: None
Cycles: 1805
Input: 0x04
DECOMPRESSION-FAILURE STATE_NOT_FOUND
Input: 0x05
Output: None
Cycles: 2057
Input: 0x06
Output: None
Cycles: 1993
A.3.3. Multiple Compartments
0xf81b 110f 8602 89a2 071c 01a0 45f9 1762 030d 3d06 1762 0537 86a0
0x6806 2289 20a1 c062 0006 0006 2203 20a1 c062 0006 0007 22a2 020a
0x2203 0622 a203 20a1 c062 0006 0020 a1c0 a206 0006 6216 2b20 a7c0
0x2000 0600 1622 1fa2 1306 0000 0000 1fa2 1906 0000 0000 1fa2 2506
0x0000 0000 1fa2 2b06 0000 0000 2300 0000 0000 0000 1762 0706 101a
0x1fa2 0706 0000 0000 16ea 1fa2 0d06 0000 0000 16e0 1fa2 1f06 0000
0x0000 169f d600 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
0x0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0102
0x0304 0506 aca6 0b8e b283 9dbf afc6 3dd2 34c5 d91d 5361 bdd6 ba2a
0xc65a 47c2 1814 ee07 c275 941d d7a1 4887 9c8d e90e
Input: 0x00
Output: None
Cycles: 1809
Input: 0x01
Output: None
Cycles: 1809
Input: 0x02
Output: None
Cycles: 1809
Input: 0x03
Output: None
Cycles: 1993
Input: 0x04
Output: None
Cycles: 1994
Input: 0x05
Output: None
Cycles: 1804
Input: 0x06
DECOMPRESSION-FAILURE STATE_NOT_FOUND
Input: 0x07
DECOMPRESSION-FAILURE STATE_NOT_FOUND
Input: 0x08
DECOMPRESSION-FAILURE STATE_NOT_FOUND
A.3.4. Accessing RFC 3485 State
0xf803 a11f a0a6 14ac fe01 2000 1fa0 a606 acff 0121 001f a0a6 0cad
0x0001 2200 2220 0323 0000 0000 0000 00fb e507 dfe5 e6aa 5af2 abb9
0x14ce aa05 f99c e61b a5
Input: None
Output: 0x5349 50
Cycles: 11
A.3.5. Bytecode State Creation
0xf804 6112 a0be 081e 2008 1e21 060a 0e23 be03 12a0 be08 a050 2008
0xa050 a053 140a 2008 a050 a053 0c0a 1606 004f 4b31 1c01 a0b3 fc22
0xa0a8 0323 0000 0da0 a8a0 ab06 0a4f 4b32 22a0 5003 2302
Input: None
Output: 0x4f4b
Cycles: 66
0xf905 b88c e72c 9103
Input: None
Output: 0x4f4b 31
Cycles: 7
0xfb24 63cd ff5c f8c7 6df6 a289 ff
Input: None
Output: 0x4f4b 32
Cycles: 5
0xf95b 4b43 d567 83
Input: None
Output: 0x0000 32
Cycles: 5
0xf9de 8126 1199 1f
Input: None
DECOMPRESSION-FAILURE STATE_NOT_FOUND
Authors' Addresses
Abigail Surtees
Siemens/Roke Manor Research
Roke Manor Research Ltd.
Romsey, Hants SO51 0ZN
UK
Phone: +44 (0)1794 833131
EMail: abigail.surtees@roke.co.uk
URI: http://www.roke.co.uk
Mark A. West
Siemens/Roke Manor Research
Roke Manor Research Ltd.
Romsey, Hants SO51 0ZN
UK
Phone: +44 (0)1794 833311
EMail: mark.a.west@roke.co.uk
URI: http://www.roke.co.uk
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