Proxy re-encryption (PRE) securely enables the re-encryption of ciphertexts from one key to another, without relying on trusted parties, i.e., it offers delegation of decryption rights. PRE allows a semi-trusted third party termed as a "proxy" to securely divert encrypted files of user A (delegator) to user B (delegatee) without revealing any information about the underlying files to the proxy. To eliminate the necessity of having a costly certificate verification process, Green and Ateniese introduced an identity-based PRE (IB-PRE). The potential applicability of IB-PRE leads to intensive research from its first instantiation. Unfortunately, till today, there is no unidirectional IB-PRE secure in the standard model, which can withstand quantum attack. In this paper, we provide, for the first time, a concrete construction of unidirectional IB-PRE which is secure in standard model based on the hardness of learning with error problem. Our technique is to use the novel trapdoor delegation technique of Micciancio and Peikert. The way we use trapdoor delegation technique may prove useful for functionalities other than proxy re-encryption as well.
Proxy re-encryption (PRE) securely enables the re-encryption of ciphertexts from one key to another, without relying on trusted parties, i.e., it offers delegation of decryption rights. PRE allows a semi-trusted third party termed as a "proxy" to securely divert encrypted files of user A (delegator) to user B (delegatee) without revealing any information about the underlying files to the proxy. To eliminate the necessity of having a costly certificate verification process, Green and Ateniese introduced an identity-based PRE (IB-PRE). The potential applicability of IB-PRE leads to intensive research from its first instantiation. Unfortunately, till today, there is no unidirectional IB-PRE secure in the standard model, which can withstand quantum attack. In this paper, we provide, for the first time, a concrete construction of unidirectional IB-PRE which is secure in standard model based on the hardness of learning with error problem. Our technique is to use the novel trapdoor delegation technique of Micciancio and Peikert. The way we use trapdoor delegation technique may prove useful for functionalities other than proxy re-encryption as well.
Abstract The concept of Proxy Re‐Encryption (PRE) was introduced by Blaze, Bleumer and Strauss at Eurocrypt in 1998. In this concept, a semi‐trusted proxy user acquires a re‐encryption key from the delegator. Then the proxy can easily convert the encrypted message under Alice's public key into an encrypted message under Bob's public key, without knowing the content of the message. For a unidirectional PRE, a master secret security (MSS) has been proposed as another security requirement by Ateniese et al. MSS provides security to the secret key of the delegator from computation by association with a malicious delegatee and dishonest proxy. In this study, first we have shown that Aono et al.'s scheme is not secure under the MSS model. Second, we have designed a unidirectional PRE scheme, based on Aono et al.'s study, and proved its security under the MSS model. In Table 2, we have shown that our scheme is more efficient in terms of computational and communication costs. Third, we have constructed a lattice‐based unidirectional PRE + scheme, similar to the scheme proposed by Wang et al. In this scheme the encryptor itself works as the delegator.
Proxy re-encryption (PRE) allows a semi-trusted party (called a proxy) to transform ciphertexts under one user's public key into ciphertexts under another user's public key, without revealing any information about the underlying messages or the secret keys. On the other hand, post-quantum cryptography (PQC) is one of the most active areas, and in particular, many lattice-based PRE schemes have been proposed so far in the area of PQC. However, there is no post-quantum PRE satisfying security against adaptive chosen ciphertext attacks ( C C A 2 security), while C C A 2 security is one of the most desirable security notions for PRE. In this paper, we propose a group-action-based PRE scheme that achieves C C A 2 security for the first time. We give security proofs for our PRE in the random oracle model (ROM) and the quantum random oracle model (QROM). In particular, we can obtain the CSIDH-instantiation of this PRE scheme as the first post-quantum PRE. Our result contributes to the developments of post-quantum cryptography, and shows further potential of isogeny-based cryptography.
Identity-based proxy re-encryption (IB-PRE) is a kind of public key cryptography that allows a proxy to convert the ciphertext based on Alice’s identity into another ciphertext of the same message for Bob. It has important applications in cloud computing, distributed systems and secure e-mail forwarding. So far, the existing lattice-based IB-PRE schemes are designed on the general lattice and their security is based on the learning with errors (LWE) assumption. In this paper, we propose an IB-PRE scheme over NTRU lattices with the desirable properties of anonymity, unidirectionality, backward collusion safeness and multi-hop. Our IB-PRE scheme is provable secure under adaptive chosen-plaintext and adaptive chosen-identity attacks. And, in the random oracle model, the security of our scheme is based on the decisional Ring-LWE assumption. Besides, the key and ciphertext sizes of our IB-PRE scheme are short, only one or two ring elements, and our scheme could encrypt n bits in each encryption process.
The proxy re-encryption allows an intermediate proxy to convert a ciphertext for Alice into a ciphertext for Bob without seeing the original message and leaking out relevant information.Unlike many prior identity based proxy re-encryption schemes which are based on the number theoretic assumptions such as large integer factorization and discrete logarithm problem.In this paper, we first propose a novel identity based proxy re-encryption scheme which is based on the hardness of standard Learning With Error(LWE) problem and is CPA secure in the standard model.This scheme can be reduced to the worst-case lattice hard problem that is able to resist attacks from quantum algorithm.The key step in our construction is that the challenger how to answer the private query under a known trapdoor matrix.Our scheme enjoys properties of the non-interactivity, unidirectionality, anonymous and so on.In this paper, we utilize primitives include G-trapdoor for lattice and sample algorithms to realize simple and efficient re-encryption.
Proxy re‐encryption (PRE) is a promising cryptographic structure for pervasive data sharing in cloud‐based social networks, which enables a semi‐trusted proxy to convert a ciphertext for Alice into a ciphertext for Bob without seeing the corresponding plaintext. Since the proxy is semi‐trust, a PRE scheme which can resist the collusion attack will be of great practical value. Jiang et al . in 2015 and Kim and Jeong in 2016 have proposed collusion‐resistant PRE (CR‐PRE) schemes from the lattice by a similar technique, respectively. However, through the analysis of their schemes, the authors find that both of them have defects in the construction of the re‐encryption key, which will lead to the re‐encryption ciphertext cannot be decrypted or decrypted error with high probability. In this study, the authors first point out the defects in the work of Jiang et al . 's work and Kim and Jeong's work and propose an improved collusion‐resistant unidirectional PRE scheme from lattice, based on learning with errors problems. In addition to solving the defects, CR‐PRE still has many useful properties similar to the previous schemes, such as unidirectional, collusion resistant, chosen‐plaintext attack secure and so on.