Analysis and Forgery Attack to Authorised Group Signature Scheme;

A new forgery attack on message recovery signatures;

A class of threshold signature scheme based on ElGamal is improved,in which dealer right can be restricted,it can prevent forgery attack for security.

Based on security analysis on Hsu scheme,an improved threshold proxy signature scheme was proposed,which effectively overcomed the disadvantage of Hsu scheme which couldn t stand the internal conspiracy attack and the forge attack.

There is forge attack in the scheme.

Security proofs of the 2~m-root identification scheme under concurrent attacks;

The experimental results demonstrate the algorithm has great robustness and unperceptiveness and can efficiently against temporal synchronization attacks and content.

Special attention is paid to the synchronization attacks, which can destroy most audio watermarking schemes with very low cost.

Synchronization attacks have more resistance than simple ones, because synchronization attacks will destroy the information-bearing data and the watermark synchronization.

Unlike traditional image watermarking, video watermarking has to deal with extra attacks, such as temporal synchronization attacks, including frame dropping, frame insertion and frame transposition, etc.