CRYPTANALYSIS OF THE HARN AND WANG MODIFICATION OF THE XINMEI DIGITAL SIGNATURE SCHEME

Xinmei has devised a digital signature scheme based on error correcting codes. Harn and Wang have observed that the combination of valid signatures produced by the Xinmei digital signature scheme yields valid signatures for other messages. Ham and Wang have proposed a modified version of the Xinmei scheme that prevents such selective forgeries. The authors of the Letter have previously shown that the Xinmei scheme can be totally broken by a chosen-ciphertext attack with complexity O(n3), where n is the length of the code used in the scheme. In the Letter it is shown that the Ham and Wang modified scheme can be broken by a known-plaintext attack with complexity O(k3).