Abstract
As a cryptography primitive for secure data transmission, certificateless proxy signcryption (CLPS) allows an original signcrypter to entrust his signing authority to a proxy signcrypter for signing specified message on his behalf. In this paper, we combine CLPS with cyclic multiplication groups (CMGs) to construct a new certificateless proxy signcryption scheme from CMGs (CMGs-CLPSS). CMGs-CLPSS will receive significant attention because it simplifies the traditional public key cryptosystem (PKC) and solves the key escrow issue suffered by identity-based public key cryptosystem (IB-PKC). In CMGs-CLPSS, an encrypted message can only be decrypted by a designated receiver who is also responsible for verifying the message; moreover, if a later dispute over repudiation occurs, the designated receiver can readily announce ordinary CLPS for public verification without any extra computation effort. CMGs-CLPSS is proved to have the indistinguishability under adaptive chosen-ciphertext attacks (IND-CCA2 security) and existential unforgeability under adaptive chosen-message attacks (UF-CMA security) in the random oracle model. CMGs-CLPSS outperforms the existing schemes on the basis of computational complexity and is suitable for applications in digital contract signing and online proxy auction, and so on.
Highlights
In traditional public key cryptosystem (PKC), the confidentiality and unforgeability are ensured by first signing the message with a sender’s private key and encrypting message-signature pair using one session key
Contributions: In this paper, we provide a construction of certificateless proxy signcryption scheme from cyclic multiplication groups (CMGs) (CMGs-CLPSS)
By comparison with the previous schemes, we find that CMGs-CLPSS is more efficient in terms of the computation complexity
Summary
In traditional PKC, the confidentiality and unforgeability are ensured by first signing the message with a sender’s private key and encrypting message-signature pair using one session key. A2 cannot extract the private key of identity Ib∗ in Phase 2 and should not submit a query to unsigncryption oracle for σ ∗ after challenge phase. A1 makes a sequence of polynomially bounded number of queries as Phase 1 in IND-CMGs-CLPSS-CCA2-I. A1 wins UF-CMGs-CLPSS-CMA-I if the result of unsigncryption is valid and the queries are subject to several restrictions as follows: x A1 cannot extract the private key of identity Ia∗; y Ia∗ cannot be an identity for which both the partial private key has been extracted and the public key has been replaced; z < Ib∗, Ip∗, m∗w, σ ∗ > should not be returned by the proxy signcryption oracle. A2 adaptively submits a polynomially bounded number of queries as Phase 1 in IND-CMGs-CLPSS-.
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