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y It utilizes the orthogonality between sinusoidal with differentfrequencies.

done in time domain;

Embedding complexity is

quite low.

5. Length of thepseudorandom sequencesused is very short.

6. Embedded sinusoids alwaysstart and end at zero

minimizes the chance of

block noise

Two-Set

Method

y Blind watermarking scheme can be created by making two setsdifferent when the two sets are different, watermark is present ; it

is a hypothesis test that typically based on the differences of means

between the two sets without the need of the original signal.

y Making two sets of audio blocks with different energies can also be apart of blind watermarking i.e. Patchwork

y Patchwork embeds special statistic into an original signal.y 2 major steps: i)choose two patches randomly and ii) add small

constant value dinto the samples of one patchA and subtract the

same value dfrom the samples of another patch B.

y Hence the original sample values need to be slightly modified.y The detection starts with the subtraction of the sample values

between two patches and the expected value of differences of the

sample means is used to decide whether the signal contain

watermark or not.

y Originally patchwork is applied in time domain data but it isvulnerable even to weak attacks and modification.

y Patchwork scheme then can be implemented in the transform-domain and it improved the original algorithm.

y New improvement: multiplicative patchwork scheme.

1. Less compleximplementation.

1. The actual difference of sample is notalways zero in practice hence there is

possibility to of wrong detection.

2. The performance of the patchworkscheme depends on the distance

between two sample means which

affect inaudibility.

3. Patchwork is originally designed forimage watermarking.

y Another method is amplitude modification which embeds thewatermark by changing energies of two or three blocks

y Basically energy w amplitude of signal.4. If the energy gap between 2 blocks is

high, the resulting artefacts become

obvious and so unnatural.

Replica Method

y Utilising original audio as an watermark embeds part of the originalsignal in frequency domain as watermark i.e. its embeds replica

(properly modulated original signal).

1. High immunity tosynchronization attack.

y One of it is echo hiding embeds data into an original audio signal by 2. Usually invinsible and make 1. High complexity due to cepstrum and

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introducing an echo or multiple echoes in time domain.

y Binary messages are embedded by echoing the original signal withone of two delays.

y Extraction of the embedded message involves the detection of delay.Autocepstrum or cepstrum detects the delay.y Time spread echo can reduce the possibility of attacks but it is more

complicated as well as auto-correlation modulation.

the sound rich.

3. Double echoes(embeddinga virtual echo by delaying

echo-embedding process)can ehance the detection

rate and enhance

imperceptibility.

auto cepstrum computation during

detection

2. Echo is easily detectable without anyprior knowledge. Hence it gives wayfor malicious attacks.

y Replica modulation is a novel watermarking technique of embeddinga replica(modified original signal).

y 3 replica modulation includes 3 modulation methods: frequency-shift, phase-shift and amplitude-shift scheme

4. 3.

The latest audio watermarking technique based on:

DiscreteWavelet Technique

Discrete Cosine Transformation