A method for obtaining digital signatures and public-key cryptosystems
Communications of the ACM
Time-Stamping with Binary Linking Schemes
CRYPTO '98 Proceedings of the 18th Annual International Cryptology Conference on Advances in Cryptology
On the design of time-stamped signatures
Journal of Computer and System Sciences
A public key cryptosystem and a signature scheme based on discrete logarithms
IEEE Transactions on Information Theory
Video steganography for confidential documents: integrity, privacy and version control
Proceedings of the 26th annual ACM international conference on Design of communication
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To ensure integrity and originality of digital information, digital signatures were proposed to provide both authority and non-repudiation. However, without an authenticated time-stamp, we can neither trust signed documents when the signers' signature key was lost, stolen, or accidentally compromised, nor solve the cases when the signer himself repudiates the signing, claiming that has accidentally lost his signature key. To withstand forward forgery suffered by linking schemes and to reduce verification cost, Sun et al. proposed four time-stamped signature schemes that are based on absolute temporal authentication. Though Sun et al. claimed that these schemes are quite secure against the forward forgery, we find that they suffered from substitution attacks, by which the signer can backward/forward forge signatures and the time-stamping service can also forge signatures. Finally, we also propose four time-stamped signature schemes to overcome these security flaws. Moreover, the proposed new schemes are more efficient than the Sun et al. schemes.