Abstract: Based on the revised LKK scheme presented by Lee et al., an improved strong proxy signature scheme is proposed. A method of blindness is used between the original signer and the proxy signer, and the construction of s_A is improved in the period of delegation. The problem that the original scheme is insecure against the original signer’s forgery attack and the original signer’s changing attack is resolved. Analysis shows that the proposed scheme satisfies all security properties of the strong proxy signature scheme and does not need a secure channel.

Key words: proxy signature, secure channel, forgery attack