On the Security of Fair Non-repudiation Protocols

A new dependable exchange protocol

“…When implementing the protocol, we follow the principles proposed by Gurgens et al [12] as briefly described below:…”

“…Also we argue that the transparent TTP will not affect the observability of our protocol. When implementing the protocols, we incorporate the label and message construction design principles proposed by Gurgens et al [12]. When using offline TTP, the problem of encrypted item validation arises and we propose two methods considering different application scenarios.…”

An Efficient Certified E-Mail Scheme Suitable for Wireless Mobile Environments

“…Therefore, if the receiver Bob denies having received a specific message from Alice, Alice can provide the publicly verifiable receipt to an arbitrator to show that this claim is untrue. Similar security services are provided by non-repudiation protocols [8], [15].…”

“…But those schemes are not optimized to reduce the number of asymmetric cryptographic operations that are required to complete a message delivery. Actually, most of those schemes [4], [10], [8], [12] need ten or more modular exponentiations, the most expensive operations in cryptography. The other two schemes proposed in [9], [11] are relatively simple, but they are vulnerable to an attack that allows the sender to cheat the receiver by mixing identities of different TTPs [15].…”