MP3 Stegonography

Lukasz Grzegorz MaciakMicheal Alexis Ponniah

Renu Sharma

Project Goal

Implement a method to embed textual data into audio files using stegonography

Embed lyrics into mp3 files Extract lyrics from an mp3 Display the lyrics while the song is

playing

Why MP3 Files?

Open Standard (as opposed to proprietary WMA)

Very Popular Preferred by end users Easily Available

FEATURES OF MP3

Designed to store audio data It’s a compressed file format It’s lossy data format meaning that

original audio signal is not retained in its entirety.

Aims to preserve the sound quality while minimizing storage space.

BASICS OF MP3 ENCODING

Takes into account the properties of HAS(Human auditory system)

Discards any sounds with frequencies out of the audible scale.

Mp3 stores only a single copy of group of similar sounding notes.

MP3 Encoding

Fragmentation: The size of the frame depends on the audio resolution or bit rate.

Perceptual Optimization: Each frame is analyzed so that frequencies that are not audible are discarded.

Huffman Compression Appending Header meta-data

MP3 Encoding

MP3 File Structure

MP3 Frame Headers

MP3 Frame Headers

Position Purpose Length

A Frame sync 11

B MPEG audio version (MPEG-1, 2, etc.) 2

C MPEG layer (Layer I, II, III, etc.) 2

D Protection (if on, then checksum follows header) 1

E Bitrate index (lookup table used to specify bitrate for this MPEG version and layer) 4

F Sampling rate frequency (44.1kHz, etc., determined by lookup table) 2

G Padding bit (on or off, compensates for unfilled frames) 1

H Private bit (on or off, allows for application-specific triggers) 1

I Channel mode (stereo, joint stereo, dual channel, single channel) 2

J Mode extension (used only with joint stereo, to conjoin channel data) 2

K Copyright (on or off) 1

L Original (off if copy of original, on if original) 1

M Emphasis (respects emphasis bit in the original recording; now largely obsolete) 2

MP3 Frame Length

Embedding Text into MP3 Files

Non-Stegonographic methods

Encode time mp3 stegonography

Post encoding mp3 stegonography

Non Stegonographic Methods

ID3v2 Comment Frame Lyrics3 Specification (ID3 extension)

Flaws of Non-Stego Methods

Increase in File Size

Not applicable to this project

Encode Time Stegonography

Low Bit Encoding

Phase Coding

Spread Spectrum Coding

Echo Data Hiding

Flaws of Encode Time Stego

Difficult to implement

Tied to single implementation of mp3 encoder/decoder

Require access to source wav files

Post Encoding Stegonography

Unused Header Bit Stuffing

Padding Byte Stuffing

Why Post Encode Stego?

Easy to implement Do not require source WAV files Can be used with an of the shelf

encoder No sound quality degradation

Implementation Choices

Implemented in Java

Stegonographic Method: Padding Byte Stuffing

Stegonographic Module as stand alone application

Stegonographic Module: Design

Flow of Control

LZW Compression

StegIO - Writing calculate the length of the message in bytes prepend the length to the message put the message on a byte queue

while(there are still bytes to be written) {

Header = read 4 bytes from the file

if(Header is_valid && contains padding byte){

seek to the end of framepop the byte from the queuewrite the popped byte into file

} }

StegIO - Reading

length = integer > 4 counter = 0 while (counter < length) {

Header = read 4 bytes from the fileif(Header is_valid && contains padding byte){

if(counter == 4){ length = to_integer ( pop 4 bytes from queue)}seek to the end of frameread a byte from the filepush the read byte onto queue

} }

Stegonographic Module: Usage

To Embed text:

java –jar mp3stego.jar mp3_file.mp3 text_file.txt

To Extract text:

java –jar mp3stego.jar mp3_file.mp3

Stegonographic Module: Comments & Future Work

Padding Byte Stuffing – problematic

Data Corruption

Java and MP3

Java Sound API

Java Media Framework

MP3 Player Implementation

Used an open source java player called Java MP3 player.

http://www.codetoad.com/java_mp3_player.asp

Text & Music Synchronization

Line starts with time offset Followed pipe character “ | ” Followed by the lyric text Line ends with a new line (“ \n ”) File terminates in hash mark (“ # “)

Sample Lyrics File

19100|May the good Lord be with you21250|Down every road you roam28300|And may sunshine and happiness31150|surround you when you're far from home

…

207790|Forever Young217240|For, forever young227050|Forever Young

#

Future Work

Implementation using Unused Header Bit Stuffing

Automating Lyrics Markup and Synchronization

Demo and Questions

References Hacker, Scot, “MP3, The Definitive Guide”, 1st Edition, March 2000, O'Reilly Publishing. Noto, Mark, MP3Stego: Hiding Text in MP3 Files, September 2001, SANS Institute. Koichi Takagi, Shigeyuki Sakazawa, Yashuiro Takishima, “Light Weight MP3 Watermarking Method for

Mobile Terminals”, KDDI R&D Labs, MM'05 November 6-11, 2005 Singapore, ACM “Huffman Code”, Wikipedia, http://en.wikipedia.org/wiki/Huffman_code M. Nilsson, “ID3 tag version 2.4.0 - Main Structure”, November 2000,

http://www.id3.org/id3v2.4.0-structure.txt Predrag Supurovic, “MPEG Audio Frame Header”, 1998 DataVoyage, http://

www.dv.co.yu/mpgscript/mpeghdr.htm#MPEGTAG “The Private Life of MP3 Frames”, http://www.id3.org/mp3frame.html M. Nilsson, “ID3 tag version 2.3.0”, February 1999, http://www.id3.org/id3v2.3.0.html Strnad Peter, Gingold Peter, “Lyrics3 Tag v2.00”, Jun 1998, http://www.id3.org/lyrics3200.html Bender W., Gruhl D., Morimoto N., Lu A., “Techniques for data hiding”, 1996, IBM,

http://www.research.ibm.com/journal/sj/353/sectiona/bender.txt Petitcolas Fabien A. P., “mp3stego”, 1997–2005,

http://www.petitcolas.net/fabien/steganography/mp3stego/ Koso A., Turi A., and Obimbo C., “Embedding Digital Signatures in MP3s”, from proceedings 477

Internet and Multimedia Systems, and Applications, 2005 Cheng Cheok Yan, “Introduction On Text Compression Using Lempel, Ziv, Welch (LZW) method”,

http://www.geocities.com/yccheok/lzw/lzw.html “LZW”, Wikipedia, http://en.wikipedia.org/wiki/LZW “Information-and-Entropy”, MIT, Spring 2003, http://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-

and-Computer-Science/6-050JInformation-and-EntropySpring2003/ABF6E960-C29C-48BB-95AE-AF9F79D9E20B/0/chapter3new.pdf

Fraunhofer-Gesellschaft, http://www.iis.fraunhofer.de/amm/techinf/layer3/index.html