AUDIO WATERMARKING AND

STEGANOGRAPHY

Anirudh Shekhawat

Manan Shah

Prateek Srivastava

Pratik Poddar

Guided by: Prof. Bernard Menezes

DIGITAL WATERMARKING

Embedding perceptually transparent data in

digital media

Watermark can be detected and retrieved by a

computer algorithm

Applications include broadcast monitoring,

fingerprinting, copyright protection and

steganography

STEGANOGRAPHY

Steganography literally means "secret writing”

Hiding data in a digital media

Avoids the suspicion and scrutiny an encrypted

message would arouse

Applications include "covert communication”

Examples from history - Invisible ink, Scalp

tattoo, Pinholes

APPLICATIONS

COPYRIGHT PROTECTION

Ownership information can be embedded in the

media

Presence of the watermark can be demonstrated

to prove ownership

The watermark must survive compression

FINGERPRINTING

Embedding a serial number in each copy of a

media before distribution

Can be used to trace down the originator of a

particular illegal copy of media

The watermark must be secure against attacks

BROADCAST MONITORING

Programs and advertisements broadcasted can be

monitored by an automated system

Illegal broadcasts can be identified by monitoring

satellite nodes

High Bit rate and low complexity are required

COVERT COMMUNICATION

Embedding data such that existence of a

watermark cannot be detected

Aimed at protecting the sender and receiver

rather than the message

Terrorists have been reported to hide messages

in images to communicate

CHARACTERISTICS OF A

WATERMARKING ALGORITHM

PERCEPTUAL TRANSPARENCY

Primary requirement in watermarking

Watermark should be imperceptible to human

auditory system

Watermarking is more difficult for audio as

compared to images

WATERMARK BIT RATE

Represented in bits per second (bps)

Required rates vary across applications (0.5 bps

in copyright protection and 15 bps in broadcast

monitoring)

Attainable values depend upon level of

compression of audio

ROBUSTNESS

The ability of the watermark to survive common

signal processing manipulations

Required against a predefined set of

manipulations

Required in some applications (radio broadcast

monitoring) but not at all required in some

(tampering detection)

BLIND AND INFORMED DETECTION

Informed: with access to original(host) audio

Blind: without access to original audio

Informed techniques are more secure

Examples

Blind: Tampering detection, Information Carrier

Informed: Steganography

SECURITY

Adversary must not be able to detect the

existence of embedded data

Not be able to extract or modify the data without

the secret key

In some cases the watermark is encrypted before

being embedded

ALGORITHMS AND DEMO

1) LEAST SIGNIFICANT BIT ENCODING

Watermark added in the least significant bit of

amplitude

Easy to embed and retrieve

High bit rate

Low robustness

WATERMARKING, COMPRESSION &

REDUNDANCY

Lossy compression destroys watermark.

To make watermark robust against compression,

we need sufficient redundancy

LSB encoding: Robustness vs Imperceptibility?

LSB Watermarking in JPEG done

Possible for MP3?

2) PHASE MODULATION

Embed watermark by modulating phase in host

audio

Robust against signal processing manipulations

Extraction or detection of watermark needs

original audio

Suitable for applications where security and

robustness are important, e.g. copyright

protection

3) FREQUENCY DOMAIN STEGANOGRAPHY

Shanon Sampling theorem

Sampling rate for CD is 44.1KHz the highest

frequency is 18KHz

Average peak frequency which a human can hear

is 18Khz

22 – 18 = 4KHz band goes unused

UNDERLYING PRINCIPLE

Use the 18Khz - 22KHz frequency band to hide

the message

Message

signal

Base

signal

Fig : Combined Signal

MERITS AND DEMERITS

Merits

Longer message can be hidden in a given base

Less likely to be affected by errors during

transmission

Demerits

Message signal has limited frequency range

Low recovery quality

4) ECHO HIDING

Embeds data by introducing “echo” in the original

signal.

Resilient to lossy data compression algorithms.

ECHO ENCODING AND DECODING

Encoding

Decoding

THE END.. QUESTIONS?

REFERENCES

Juergen Seitz, Digital Watermarking for Digital Media, ISBN

159140519X, 2005, Information Resources Press, Arlington, VA,

USA

Nedeljko Cvejic, Algorithms for audio watermarking and steganography, ISBN 9514273834, 2004, Oulu University Press,

Oulu

C.H. Yeh & C.J Kuo, Digital watermarking through quasi m-arrays, Proceedings of the IEEE Workshop on Signal Processing Systems 1999, 456-461

Guy Belloch, Introduction to Data Compression, Draft version, Algorithms in the real world

Kuo S, Johnston J, Turin W & Quackenbush S Covert audio-watermarking using perceptually tuned signal independent

multiband phase modulation, IEEE International Conference on

Acoustics, Speech, and Signal Processing 2002, 1753-1756

REFERENCES

Foo, S.W., Yeo, T.H., & Huang, D.Y. (2001). An adaptive audio

watermarking system. Proceedings of the IEEE Region 10

International Conference on Electrical and Electronic Technology,

509–513.

Huang, D.Y., & Yeo, Y.H. (2002). Robust and inaudible multi-echo

audio watermarking. Proceedings of the IEEE Pacific-Rim Conference

on Multimedia, 615–622.

Bender, W., Gruhl D. Echo Hiding, International Workshop on

Information Hiding, 1996.