Signcryption with Proxy Re-encryption
Confidentiality and authenticity are two of the most fundamental problems in cryptography. Many applications require both confidentiality and authenticity, and hence an efficient way to get both together was very desirable. In 1997, Zheng proposed the notion of ``signcryption'', a single primitive which provides both confidentiality and authenticity in a way that's more efficient than signing and encrypting separately. Proxy re-encryption is a primitive that allows a semi-trusted entity called the ``proxy'' to convert ciphertexts addressed to a ``delegator'' to those that can be decrypted by a ``delegatee'', by using some special information given by the delegator, called the ``rekey''. In this work, we propose the notion of signcryption with proxy re-encryption (SCPRE), and motivate the same. We define security models for SCPRE, and also propose a concrete unidirectional, non-interactive identity-based SCPRE construction. We also provide complete proofs of security for the scheme in the security models defined. We finally provide directions for further research in this area.