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Table 2 Attack types and specifications

From: Effective blind speech watermarking via adaptive mean modulation and package synchronization in DWT domain

Item

Type

Description

A

Resampling

Conducting downsampling to 8 kHz and then upsampling back to 16 kHz.

B

Requantization

Quantizing the watermarked signal to 8 bits/sample and then back to 16 bits/sample.

C

Low-pass filtering (I)

Applying a low-pass filter with a cutoff frequency of 4 kHz.

D

Low-pass filtering (II)

Applying a low-pass filter with a cutoff frequency of 1 kHz.

E

High-pass filtering

Applying a high-pass filter with a cutoff frequency of 1 kHz.

F

Amplitude scaling

Scaling the amplitude of the watermarked signal by 0.85.

G

Noise corruption (I)

Adding zero-mean white Gaussian noise to the watermarked audio signal with SNR = 30 dB.

H

Noise corruption (II)

Adding zero-mean white Gaussian noise to the watermarked audio signal with SNR = 20 dB.

I

DA/AD conversion

Converting the digital audio file to an analog signal and then resampling the analog signal at 16 kHz. The DA/AD conversion is performed through an onboard Realtek ALC892 audio codec, of which the line-out is linked with the line-in using a cable line during playback and recording.

J

Echo addition

Adding an echo signal with a delay of 50 ms and a decay to 5% to the watermarked audio signal.

K

Jittering

Randomly deleting or adding one sample for every 100 samples within each frame.

L

G.722 speech coding

Encoding and decoding the watermarked speech signal with a G.722 wideband audio codec at 64 kbps.

M

G.726 speech coding

Encoding and decoding the watermarked speech signal with a G.726 wideband audio codec at 32 kbps.

N

Time-shift by 1 sample

Purposely shifting the watermarked audio signal by one sample.