Efficient convertible authenticated encryption schemes for smart card applications in network environments

Authenticated encryption schemes allow the signer to produce an encrypted message such that only the designated recipient can recover the message and validate its signature in network environments. To avoid a later dispute on the repudiation of the signature, we should equip the recipient with the ability for converting the signature into an ordinary one which can be verified by anyone. The scheme with the above capability is called a convertible authenticated encryption (CAE) scheme. Achieving not only the requirements of integrity, authenticity and non-repudiation but also confidentiality, a CAE scheme is suitable for some practical environments such as the transmission of credit card information or the delivery of confidential documents. In the paper, we first give variants of Wu and Hsu's CAE scheme based on the discrete logarithms. Then, for facilitating the device with limited computing power and insufficient storage space like smart cards, we modify the schemes based on the elliptic curve discrete logarithms.