In a proxy re-encryption scheme, a semi-trusted proxy converts a ciphertext for Alice into a ciphertext for Bob without seeing the underlying plaintext. A number of solutions have been proposed in public key settings. Hierarchical identity-based cryptography is a generalization of identity-based encryption that mirrors an organizational hierarchy, which allows a root private key generator to distribute the workload by delegating private key generation and identity authentication to lower-level private key generators. In this paper, we propose a hierarchical identity-based proxy re-encryption (HIBPRE) scheme which achieves IND-PrID-CCA2 security without random oracles. This is the first HIBPRE scheme up to now, and our scheme satisfies unidirectionality, non-interactivity and permits multiple re-encryptions.
In a proxy re-encryption scheme, a semi-trusted proxy converts a ciphertext for Alice into a ciphertext for Bob without seeing the underlying plaintext. A number of solutions have been proposed in public key settings. Hierarchical identity-based cryptography is a generalization of identity-based encryption that mirrors an organizational hierarchy, which allows a root private key generator to distribute the workload by delegating private key generation and identity authentication to lower-level private key generators. In this paper, we propose a hierarchical identity-based proxy re-encryption (HIBPRE) scheme which achieves IND-PrID-CCA2 security without random oracles. This is the first HIBPRE scheme up to now, and our scheme satisfies unidirectionality, non-interactivity and permits multiple re-encryptions.
In an identity-based proxy re-encryption scheme, a semi-trusted proxy can convert a ciphertext under Alice's public identity into a ciphertext for Bob.The proxy does not know the secret key of Alice or Bob, and also does not know the plaintext during the conversion.In identity-based proxy re-encryption, the collusion of the proxy and a delegatee may result in the decryption of ciphertext for delegator.In this paper, we present a new scheme which can avoid the collusion of proxy and delegatee.Our scheme improves the scheme of Chu and Tzeng while inheriting all useful properties such as unidirectionality and non-interactivity.In our scheme, we get the security by using added secret parameter and change the secret key and re-encryption key.Our sheme is secure against Chosen-Ciphertext Attack (CCA) and collusion attack in the standard model.
Blaze et al. in 1998 introduced the concept of proxy re-encryption, which allows a proxy to transform a ciphertext computed under Alice's public key into one that can be opened under Bob's decryption key. In CCS'07, Canetti et al. proposed an IND-PRE-CCA2 bidirectional proxy re-encryption scheme, and later, Libert et al. proposed another IND-PRE-CCA2 secure unidirectional proxy re-encryption. However, both schemes rely on the costly bilinear pairings. In CANS'08, Deng et al. proposed the first IND-PRE-CCA2 secure proxy re-encryption without parings. Later, in PKC'09, Shao et al. proposed another IND-PRE-CCA2 secure proxy re-encryption without parings. But both of these schemes prove their security in the random oracle. In this paper, based on Hanaoka's efficient chosen ciphertext secure public key encryption under the computational Diffie-Hellman assumption, we present two new interesting bidirectional proxy re-encryption schemes, which are restricted IND-PRE-CCA2 secure without pairing nor random oracle.
In proxy re-encryption (PRE), a semi-trusted proxy can convert a ciphertext originally intended for Alice into one which can be decrypted by Bob, while the proxy cannot know the corresponding plaintext. PRE can be classified as single-use PRE and multi-use PRE according to the times the ciphertext can be transformed. In multi-use PRE schemes, the ciphertext can be transformed from A to B and to C and so on. In CCS’09 (post session), Wang et al. proposed a multi-use unidirectional CCA-secure proxy re-encryption scheme. Unfortunately, we show their proposal is not CCA-secure in the corresponding security models by giving concrete attacks. In 2010, Ren et al. proposed a hierarchical identity-based proxy re-encryption scheme without random oracles, and claimed their scheme was also multi-use and CCA-secure, we also show their scheme is not secure.
A proxy re-encryption scheme allows Alice to temporarily delegate the decryption rights to Bob via a proxy. Alice gives the proxy a re-encryption key so that the proxy can convert a ciphertext for Alice into the ciphertext for Bob. Recently, ID-based proxy re-encryption schemes are receiving considerable attention for a variety of applications such as distributed storage, DRM, and email-forwarding system. And a non-interactive identity-based proxy re-encryption scheme was proposed for achieving CCA-security by Green and Ateniese. In the paper, we show that the identity-based proxy re-encryption scheme is unfortunately vulnerable to a collusion attack. The collusion of a proxy and a malicious user enables two parties to derive other honest users' private keys and thereby decrypt ciphertexts intended for only the honest user. To solve this problem, we propose two ID-based proxy re-encryption scheme schemes, which are proved secure under CPA and CCA in the random oracle model. For achieving CCA-security, we present self-authentication tag based on short signature. Important features of proposed scheme is that ciphertext structure is preserved after the ciphertext is re-encrypted. Therefore it does not lead to ciphertext expansion. And there is no limitation on the number of re-encryption.
In a proxy re-encryption system, a semi-trusted proxy can convert a ciphertext originally intended for Alice into one encrypting the same plaintext for Bob without seeing the underlying plaintext.However, a fine-grained delegation is demanded in some scenarios.For this, Weng et al. introduce the notion of conditional proxy re-encryption (CPRE), and formalize its security model and propose an efficient CPRE scheme.This paper presents the notion of identity-based multi-condition proxy re-encryption, which is a variant of identity-based condition proxy re-encryption.In such system, ciphertexts are generated under specified conditions by Alice, and the proxy can translate the ciphertext if the relevant conditions are satisfied.We formalize its security model and construct a concrete multi-condition proxy re-encryption scheme, and prove its security in the standard model.
In 1998, Blaze, Bleumer, and Strauss proposed a kind of cryptographic primitive called proxy re-encryption. In proxy re-encryption, a proxy can transform a ciphertext computed under Alice’s public key into one that can be opened under Bob’s decryption key. In 2007, Matsuo proposed the concept of four types of proxy re-encryption schemes: CBE (Certificate Based Public Key Encryption) to IBE (Identity Based Encryption) (type 1), IBE to IBE (type 2), IBE to CBE (type 3), CBE to CBE (type 4). In this paper, we find that if we allow the PKG to use its masterkey in the process of generating re-encryption key for proxy re-encryption in identity based setting, many open problems can be solved. We give the new security models for proxy reencryption in identity based setting, especially considering PKG’s involving in the re-encryption key generation process and PKG’s master-key’s security. We construct the new IND-ID-CPA and the first IND-ID-CCA2 secure proxy reencryption schemes based on BB1 IBE. We also prove their security by introducing some new techniques which maybe have independent interest. At last, we compare our new schemes with existing ones, the results show that our scheme can achieve high security levels and are very efficient for re-encryption and, which are very important for practical applications.