An Efficient Forward Secure Authenticated Encryption Scheme with Ciphertext Authentication Based on Two Hard Problems

Abstract

Authenticated encryption is a cryptographic technique that concurrently establishes message confidentiality, integrity, authenticity and non-repudiation. In this paper, an efficient authenticated encryption scheme is proposed, based on the hardness of the integer factorization problem and the discrete logarithm problem on conic curves over a ring \(Z_n\). The protocol provides forward secrecy in case the sender’s private keys are compromised and supports public verifiability, as well as, ciphertext authentication by an external verifier, without full decryption. Hence, the protocol can be used for secure data sharing in untrusted cloud environments. Several attack scenarios against the scheme are analysed to confirm its validity as an authenticated encryption protocol. The security criterions are satisfied, as long as either one of the hardness assumptions hold. The scheme is implemented over conic curves, which possess interesting characteristics like effective message encoding and decoding, easily computable point operations and inverses.