ID-based message recovery signature is a kind of lightweight signature. In such a signature scheme, a complicated certification system is discarded and the total length of the message and the appended signature is also shortened. Proxy signature allows an original signer to delegate a proxy signer to sign messages on its behalf, which has found numerous practical applications such as grid compu...

Abstract A (t, n) threshold proxy signature scheme enables an original signer to delegate the signature authority to a proxy group of n member such that t or more than t proxy signers can cooperatively sign messages on behalf of the original signer. In the paper, we review the security of some nonrepudiable threshold proxy signature schemes with known signers. We show that Sun’s threshold proxy...

Signature used as a biometric is implemented in various systems as well as every signature signed by each person is distinct at the same time. So, it is very important to have a computerized signature verification system. In offline signature verification system dynamic features are not available obviously, but one can use a signature as an image and apply image processing techniques to make an...

To enhance the efficiency of threshold group signature schemes, Yu and Chen, recently, proposed an efficient threshold group signature scheme. By using elliptic curves, the proposed scheme can use short secret key and reduces the load of signature verification. However, in this paper we find that there are many ambiguities in the proposed scheme. The verifiers cannot verify valid signatures, wh...

Polyphase is a common class of pulse compression waveforms in the radar systems. Oppermann code is one of the used codes with polyphone pattern. After compression, this code has little tolerant against Doppler shift in addition to its high side lobe level. This indicates that the use of Oppermann code is an unsuitable scheme to radars applications. This paper shows that the use of amplitude wei...

 Using the concept of system signature introduced by Samaniego (1985), Kochar et al. (1999) compared the lifetimes of the systems in which the lifetimes of the components are independent and identically distributed (i.i.d.) random variables. Their results are extended to the systems with exchangeable components by Navarro et al. (2005). This paper gives some alternative proofs to obtain th...

A group signature scheme allows a group member of a given group to sign messages on behalf of the group in an anonymous fashion. In case of a dispute, however, a designated group manager can reveal the signer of a valid group signature. In the paper, we show the untraceability of two group signatures in [1, 5] by new and very simple attacks. Although those flaws, such as, forgeability, untracea...

Proxy signature is a signature that an original signer delegates his or her signing capability to a proxy signer, and then the proxy signer creates a signature on behalf of the original signer. However, Sun et al. [7] showed that the proxy and multi-proxy signatures of Lee et al. [3], and the strong proxy signature scheme with proxy signer privacy protection of Shum et al. [6] are not against t...

Résumé. Cet article concerne la découverte de signatures (ou modèles de chroniques) à partir d’une séquence d'événements discrets (alarmes) générée par un agent cognitif de surveillance (Monitoring Cognitive Agent ou MCA). Considérant un couple (Processus, MCA) comme un générateur stochastique d’événements discrets, deux représentations complémentaires permettent de caractériser les propriétés ...