Volume 14, Issue 4 (2003), pp. 445–454
An authenticated encryption allows the designated recipient to verify the authenticity while recovering the message. To protect the recipient's benefit in case of a later dispute, a convertible authenticated encryption scheme allows the recipient to convert the authenticated encryption into an ordinary signature so that it becomes a publicly verifiable. This paper shows a universal forgery attack on Araki et al.'s convertible authenticated encryption scheme, and proposes a new convertible authenticated encryption scheme. Without using any conventional one‐way function, the proposed scheme simplifies its security assumption on only a public hard problem – the discrete logarithm problem.
Volume 14, Issue 2 (2003), pp. 155–166
A partially blind signature scheme allows the signer to inoculate a non‐removable common information into his blind signature. This common information may represent the date or the amount of e‐cash. Due to its un‐traceablility and partial blindness property, the partially blind signature plays an important role in many e‐commerce applications. Based on the RSA scheme, we propose a partially blind threshold signature with low‐computational load for the client.