A Novel (t,n) Threshold Convertible Authenticated Encryption Scheme

Authenticated encryption schemes allow the signer to generate an authenticated ciphertext such that only the designated recipient has the ability to recover the message and verify its corresponding signature. It can be seen that authenticated encryption schemes are applicable to lots of E-Commerce applications like credit card transactions, since these schemes simultaneously fulfill the security requirements of integrity, authenticity, confidentiality and non-repudiation. For more extended applications, an alternative designed for multi-user setting is necessary. In this paper, we propose a novel group-oriented authenticated encryption scheme called the (t, n) threshold convertible authenticated encryption (TCAE) scheme. The (t, n)-TCAE scheme can allow any t or more of n signers cooperatively to produce a valid authenticated ciphertext on behalf of the original group while less than or equal to t − 1 can not. Further, when the case of a later dispute over repudiation occurs, the designated recipient has the ability to convert the signature into an ordinary one for convincing anyone of the signers’ dishonesty.