Wei-Hua He

New proxy multi-signature scheme

In 2000, Yi et al.s proposed two proxy multi-signature schemes which enable some original signers to delegate their signing power to the proxy signer. However, their schemes suffer from some drawbacks. To improve the performance, this paper presented a new proxy multi-signature scheme. As compared with Yi et al.s scheme, the proposed one requires less computational efforts and communication costs. Our proposed scheme has the properties that the size of a proxy signature is independent of the number of the original signers, and the validity of a proxy signature and public keys can be verified simultaneously.

Weaknesses in some multisignature schemes for specified group of verifiers

The author points out that Laih and Yens multisignature scheme and Hwang, Chen and Changs multisignature scheme do not satisfy their security requirements.

Security of generalized signature scheme based on discrete logarithms and factorization

In 2005, Pon et al. proposed a generalized signature scheme based on the intractability of solving two well-known cryptographic assumptions, the factorization (FAC) and the discrete logarithm problem (DLP). They claimed that their scheme is still secure, provided that one of these two assumptions is solved. This paper, however, will show that Pon et al.s scheme is insecure against the universal forgery attack if the adversary can solve the DLP.

Remarks on Using RSA With Low Exponent in a Public Network

The authors give a counterexample to show that the RSA-based cryptosystem with low exponent proposed by Lee and Chang (Computer Communications 21 (1998)) is vulnerable to the low exponent attack with respect to their suggested lower boundary for the size of the public encryption key. That is, an eavesdropper can recover the plaintext from the ciphertext without knowing the secret decryption key, even though the size of the secret decryption key is large enough. The authors also suggest a new lower boundary for the size of the public encryption key for the Lee-Chang cryptosystem to enforce secrecy.