Cipher text-Policy Attribute-Based Proxy Re-Encryption (CP-ABPRE) extends the traditional Proxy Re-Encryption (PRE) by allowing a semi-trusted proxy to transform a cipher text under an access policy to the one with the same plaintext under another access policy (i.e. attribute-based re-encryption). The proxy, however, learns nothing about the underlying plaintext. CP-ABPRE has many real world applications, such as fine-grained access control in cloud storage systems and medical records sharing among different hospitals. Previous CP-ABPRE schemes leave how to be secure against Chosen-Cipher text Attacks (CCA) as an open problem. This paper, for the first time, proposes a new CP-ABPRE to tackle the problem. The new scheme supports attribute-based re-encryption with any monotonic access structures. Despite our scheme is constructed in the random oracle model, it can be proved CCA secure under the decisional q-parallel bilinear Diffie-Hellman exponent assumption.

/pdf/a-ciphertext-policy-attribute-based-proxy-re-encryption-with-10b2jctkip.pdf

A Ciphertext-Policy Attribute-Based Proxy Re-encryption with Chosen-Ciphertext Security

To date, the growth of electronic personal data leads to a trend that data owners prefer to remotely outsource their data to clouds for the enjoyment of the high-quality retrieval and storage service without worrying the burden of local data management and maintenance. However, secure share and search for the outsourced data is a formidable task, which may easily incur the leakage of sensitive personal information. Efficient data sharing and searching with security is of critical importance. This paper, for the first time, proposes a searchable attribute-based proxy reencryption system. When compared with the existing systems only supporting either searchable attribute-based functionality or attribute-based proxy reencryption, our new primitive supports both abilities and provides flexible keyword update service. In particular, the system enables a data owner to efficiently share his data to a specified group of users matching a sharing policy and meanwhile, the data will maintain its searchable property but also the corresponding search keyword(s) can be updated after the data sharing. The new mechanism is applicable to many real-world applications, such as electronic health record systems. It is also proved chosen ciphertext secure in the random oracle model.

/pdf/searchable-attribute-based-mechanism-with-efficient-data-4637248840.pdf

Searchable Attribute-Based Mechanism With Efficient Data Sharing for Secure Cloud Storage

Proxy Re-Encryption (PRE) is a useful cryptographic primitive that allows a data owner to delegate the access rights of the encrypted data stored on a cloud storage system to others without leaking the information of the data to the honest-but-curious cloud server. It provides effectiveness for data sharing as the data owner even using limited resource devices (e.g. mobile devices) can offload most of the computational operations to the cloud. Since its introduction many variants of PRE have been proposed. A Ciphertext-Policy Attribute-Based Proxy Re-Encryption (CP-ABPRE), which is regarded as a general notion for PRE, employs the PRE technology in the attribute-based encryption cryptographic setting such that the proxy is allowed to convert an encryption under an access policy to another encryption under a new access policy. CP-ABPRE is applicable to many network applications, such as network data sharing. The existing CP-ABPRE systems, however, leave how to achieve adaptive CCA security as an interesting open problem. This paper, for the first time, proposes a new CP-ABPRE to tackle the problem by integrating the dual system encryption technology with selective proof technique. Although the new scheme supporting any monotonic access structures is built in the composite order bilinear group, it is proven adaptively CCA secure in the standard model without jeopardizing the expressiveness of access policy. We further make an improvement for the scheme to achieve more efficiency in the re-encryption key generation and re-encryption phases. This paper proposes a new Ciphertext-Policy Attribute-Based Proxy Re-Encryption scheme.The scheme is proved adaptively chosen ciphertext secure by leveraging dual system encryption technology and selective proof technique.The paper also proposes an improvement for re-encryption key generation and re-encryption phases so as to reduce computational and communication cost.

A secure and efficient Ciphertext-Policy Attribute-Based Proxy Re-Encryption for cloud data sharing

Identity-based encryption (IBE) eliminates the necessity of having a costly certificate verification process. However, revocation remains as a daunting task in terms of ciphertext update and key update phases. In this paper, we provide an affirmative solution to solve the efficiency problem incurred by revocation. We propose the first cloud-based revocable identity-based proxy re-encryption (CR-IB-PRE) scheme that supports user revocation but also delegation of decryption rights. No matter a user is revoked or not, at the end of a given time period the cloud acting as a proxy will re-encrypt all ciphertexts of the user under the current time period to the next time period. If the user is revoked in the forthcoming time period, he cannot decrypt the ciphertexts by using the expired private key anymore. Comparing to some naive solutions which require a private key generator (PKG) to interact with non-revoked users in each time period, the new scheme provides definite advantages in terms of communication and computation efficiency.

/pdf/an-efficient-cloud-based-revocable-identity-based-proxy-re-5293lm1v5r.pdf

An Efficient Cloud-Based Revocable Identity-Based Proxy Re-encryption Scheme for Public Clouds Data Sharing

An Efficient Cloud-based Revocable Identity-based Proxy Re-encryption Scheme for Public Clouds Data Sharing

In ciphertext policy attribute based encryption (ABE) schemes the sender selects an access structure and generates a ciphertext,which decryptors can get plaintext if he has certain set of secret key associate with his attributeswhich satisfies the access structure. On the other hand, many organisations already introduced standard identity based encryption (IBE) or public key encryption (PKE) where only a single recipient is specified at the time of encryption. To utilize the above schemes and to simplify the management of user's key, it is valuable to develop a proxy re-encryption schemes between ABE schemes and IBE schemes. In this paper we propose the first proxy re-encryption scheme, which can convert an ABE ciphertext to a ciphertext which is encrypted by IBE scheme. Using new proxy re-encryption scheme, some useful applications can be constructed. Furthermore, we prove the security in the standard model based on decisional bilinear Diffie-Hellman assumption.

Hybrid proxy re-encryption scheme for attribute-based encryption

In proxy re-encryption schemes, a semi-trusted entity called a proxy can convert a ciphertext encrypted for Alice into a new ciphertext for Bob without seeing the underlying plaintext Several proxy re-encryption schemes have been proposed, however, only two schemes which enables the conversion of IBE ciphertexts to PKE ciphertexts has been proposed One of schemes has some drawbacks such that the size of the re-encrypted ciphertext increases and Bob must be aware of existence of the proxy, which means Bob cannot decrypt a re-encrypted ciphertext with same PKE decryption algorithm The other one achieves security under Selective-ID model We propose a new, efficient scheme that enables the conversion of IBE ciphertexts to PKE ciphertexts, and prove full-ID CPA security in the standard model In our scheme, the size of the re-encrypted ciphertext is optimal and Bob should not aware of existence of the proxy As far as we know, this is the first IBE-PKE type scheme that holds the above properties

Secure and Efficient IBE-PKE Proxy Re-Encryption

In proxy re-encryption schemes, a semi-trusted entity called proxy can convert a ciphertext encrypted for Alice into a new ciphertext for Bob without seeing the underlying plaintext. Several proxy re-encryption schemes have been proposed, however, only one scheme which enables the conversion of IBE ciphertexts to PKE ciphertexts has been proposed and it has some drawbacks. In that scheme, the size of the re-encrypted ciphertext increases and Bob must be aware of existence of the proxy, which means Bob cannot decrypt a re-encrypted ciphertext with same PKE decryption algorithm. We propose a new, efficient scheme that enables the conversion of IBE ciphertexts to PKE ciphertexts, and prove CPA security in the standard model. In our scheme, the size of the re-encrypted ciphertext is optimal and Bob does not aware of existence of the proxy. As far as we knows, this is the first IBE-PKE type scheme that holds the above properties.

Takeo Mizuno

Papers

Hybrid proxy re-encryption scheme for attribute-based encryption

Secure and Efficient IBE-PKE Proxy Re-Encryption

Efficient ibe-pke proxy re-encryption