MP3Stego
--------
Fabien A.P. Petitcolas, Computer Laboratory, Cambridge
August 1998
When looking at the steganographic tools available on the Net, it occurred to me
that nothing had been done to hide information in MP3 files, that is sound
tracks compressed using the MPEG Audio Layer III format. There is a growing
interest world-wide in MP3 files because they offer near-CD quality at
compression ratio of 11 to 1 (128 kilobits per second). This gives a very good
opportunity for information hiding.
MP3Stego will hide information in MP3 files during the compression process. The
data is first compressed, encrypted and then data hidden in the MP3 bit stream.
Although MP3Stego has been written with steganographic applications in mind it
might be used as a watermarking system for MP3 files. Any opponent can
uncompress the bit stream and recompress it; this will delete the hidden
information -- actually this is the only attack we know yet -- but at the
expense of severe quality loss.
The hiding process takes place at the heart of the Layer III encoding process
namely in the inner_loop. The inner loop quantizes the input data and increases
the quantizer step size until the quantized data can be coded with the available
number of bits. Another loop checks that the distortions introduced by the
quantization do not exceed the threshold defined by the psycho acoustic model.
The part2_3_length variable contains the number of main_data bits used for
scalefactors and Huffman code data in the MP3 bit stream. We encode the bits
as its parity by changing the end loop condition of the inner loop. Only
randomly chosen part2_3_length values are modified; the selection is done
using a pseudo random bit generator based on SHA-1.
We have discussed earlier the power of parity for information hiding [1].
MP3Stego is a practical example of it. There is still space for improvement
but I thought that some people might be interested to have a look at it.
The full C code and binaries (Makefiles for Linux or project definitions
for Microsoft Developer Studio 5) are available from:
<http://www.cl.cam.ac.uk/~fapp2/steganography/mp3stego/>
Usage exemple:
encode -E data.txt sound.wav sound.mp3
compresses sound.wav and hides data.txt. This produces the output called
sound.mp3
decode -X sound.mp3
uncompresses sound.mp3 into sound.mp3.pcm and attempt to extract hidden
information. The hidden message is decrypted, uncompress and saved into
sound.mp3.txt.
Don't forget to let me know your suggestions and comments: fapp2@cl.cam.ac.uk
This computer program is based on:
- 8hz-mp3 0.2b -- 8Hz implementation of MP3 encoder;
- MP3 Decoder (dist10) of the ISO MPEG Audio Subgroup Software Simulation Group;
- ZLib 1.1.3 compression library by Jean-Loup Gailly�s ZLib;
- Eric�s Young implementation of 3DES;
- James J. Gillogly�s implementation of SHA-1;
- ISO/IEC 11172-3:1993, Information technology -- Coding of moving pictures
and associated audio for digital storage media at up to about 1,5 Mbit/s --
Part 3: Audio, with the permission of ISO. Copies of this standards can be
purchased from the British Standards Institution, 389 Chiswick High Road,
GB-London W4 4AL, Telephone:+ 44 181 996 90 00, Telefax:+ 44 181 996 74 00
or from ISO, postal box 56, CH-1211 Geneva 20, Telephone +41 22 749 0111,
Telefax +4122 734 1079. Copyright remains with ISO.
[1] Ross J. Anderson and Fabien A.P. Petitcolas. On The Limits of
Steganography. IEEE Journal of Selected Areas in Communications,
16(4):474-481, May 1998. Special Issue on Copyright & Privacy Protection.
ISSN 0733-8716.
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MP3Stego_1_1_15.rar_MPEG-1
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MP3Stego_1_1_15.rar_MPEG-1 (122个子文件)
Readme.1st 5KB
zlib.3 3KB
README.8hz-mp3 6KB
libz.a 53KB
decode.c 69KB
l3loop.c 53KB
common.c 46KB
deflate.c 44KB
trees.c 42KB
ieeefloat.c 28KB
musicout.c 27KB
tables.c 26KB
l3bitstream.c 24KB
l3psy.c 22KB
inftrees.c 16KB
example.c 16KB
gzio.c 16KB
huffman.c 16KB
bitstream.c 15KB
formatBitstream.c 15KB
tools.c 14KB
infblock.c 13KB
ieeefloat.c 11KB
huffman.c 11KB
des_enc.c 9KB
inflate.c 9KB
stego.c 9KB
set_key.c 8KB
minigzip.c 8KB
portableio.c 8KB
infcodes.c 8KB
portableio.c 7KB
crc32.c 7KB
layer3.c 7KB
main.c 7KB
inffast.c 6KB
ede_enc.c 6KB
sha.c 6KB
fft.c 5KB
reservoir.c 5KB
zutil.c 5KB
l3mdct.c 5KB
wave.c 5KB
l3subband.c 3KB
maketree.c 2KB
infutil.c 2KB
uncompr.c 2KB
compress.c 2KB
adler32.c 1KB
error.c 990B
ChangeLog 23KB
Make_vms.com 4KB
configure 23KB
configure 7KB
README.Development 5KB
dewindow 11KB
FAQ 2KB
psy_data.h 57KB
sqrttab.h 52KB
zlib.h 36KB
common.h 21KB
des_locl.h 16KB
des.h 11KB
deflate.h 10KB
spr.h 10KB
sk.h 10KB
decoder.h 10KB
inffixed.h 9KB
trees.h 8KB
zconf.h 5KB
zutil.h 5KB
formatBitstream.h 5KB
podd.h 4KB
portableio.h 4KB
portableio.h 4KB
infutil.h 4KB
sha.h 3KB
ieeefloat.h 3KB
ieeefloat.h 3KB
bitstream.h 3KB
inftrees.h 2KB
huffman.h 2KB
types.h 2KB
tools.h 2KB
layer3.h 1KB
l3psy.h 1KB
infblock.h 1KB
stego.h 1KB
infcodes.h 764B
huffman.h 754B
l3bitstream.h 686B
l3loop.h 581B
inffast.h 505B
resource.h 412B
reservoir.h 391B
error.h 277B
tables.h 271B
l3mdct.h 271B
l3subband.h 239B
fft.h 213B
共 122 条
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