This paper shows a generic and simple conversion from weak asymmetric and symmetric encryption schemes into an asymmetric encryption scheme which is secure in a very strong sense- indistinguishability against adaptive chosen-ciphertext attacks in the random oracle model. In particular, this conversion can be applied efficiently to an asymmetric encryption scheme that provides a large enough coin space and, for every message, many enough variants of the encryption, like the ElGamal encryption scheme.

Secure integration of asymmetric and symmetric encryption schemes

Identity-based Cryptography in Public Key Management

A proxy re-encryption scheme (PRE) allows a semi-trusted proxy to convert a ciphertext encrypted under one key into a ciphertext encrypted under another key without leaking the underlying plaintext. In the process of the arithmetic processing, proxy should be able to learn as little information about the plaintext as possible. Conditional proxy re-encryption (CPRE) is a new cryptography primitive which only those ciphertexts satisfying one condition set by the delegator can be re-encrypted correctly by the proxy. In this paper, we first propose the formal definition and security model of certificate-based conditional proxy re-encryption. Further, we combine the conditional proxy re-encryption with certificate-based encryption and present a certificate-based conditional proxy re-encryption scheme. The proposed scheme is proved secure against chosenciphertext attack (CCA) in the random oracle model. Security of the scheme is reduced to the intractability of the bilinear Diffie-Hellman problem. Finally, we give the efficiency analysis of our scheme.

Provably Secure Certificate-based Conditional Proxy Re-encryption.

A proxy re-encryption scheme (PRE) allows a semi-trusted proxy to convert a ciphertext encrypted under one key into an encryption of the same plaintext under another key. In the process of the arithmetic processing, proxy should be able to learn as little information about the plaintext as possible. Conditional proxy re-encryption (CPRE) is a primitive which only those ciphertexts satisfying one condition set by the delegator can be re-encrypted correctly by the proxy. In this paper, we combine the conditional proxy re-encryption with certificate-based encryption and propose a certificate-based conditional proxy re-encryption scheme. The proposed scheme is proved secure against chosen-ciphertext security (CCA) in the random oracle model.

Certificate-Based Conditional Proxy Re-Encryption

Certificate-based forward security signature method and system thereof

Certificate-based encryption (CBE) is a new paradigm which overcomes the shortcomings of traditional public-key encryption (PKE) and identity based encryption (IBE). CBE provides an efficient implicit certificate mechanism to eliminate third-party queries for the certificate status and to simplify the certificate revocation problem in traditional PKI. Therefore, CBE can be used to construct an efficient PKI requiring fewer infrastructures. It also solves the key escrow and key distribution problem inherent in IBE. In this paper, we introduce a new notion called Forward-Secure Certificate-Based Encryption. It preserves the advantages of CBE such as implicit certificate and no private key escrow. At the same time it also inherits the properties of the forward-secure public key encryption. We also propose a concrete and efficient forward-secure CBE scheme and prove it to be secure based on the bilinear Diffie-Hellman assumption in the random oracle model.

Yang Lu

Papers

Forward-Secure Certificate-Based Encryption