Efficient Conditional Proxy Re-encryption with Chosen-Ciphertext Security

Recently, a variant of proxy re-encryption, named conditional proxy re-encryption (C-PRE), has been introduced. Compared with traditional proxy re-encryption, C-PRE enables the delegator to implement fine-grained delegation of decryption rights, and thus is more useful in many applications. In this paper, based on a careful observation on the existing definitions and security notions for C-PRE, we reformalize more rigorous definition and security notions for C-PRE. We further propose a more efficient C-PRE scheme, and prove its chosenciphertext security under the decisional bilinear Diffie-Hellman (DBDH) assumption in the random oracle model. In addition, we point out that a recent C-PRE scheme fails to achieve the chosen-ciphertext security

A Type-and-Identity-based Proxy Re-Encryption Scheme and its Application in Healthcare

Proxy re-encryption is a cryptographic primitive developed to delegate the decryption right from one party (the delegator) to another (the delegatee). In a proxy re-encryption scheme, the delegator assigns a key to a proxy to re-encrypt all messages encrypted with his public key such that the re-encrypted ciphertexts can be decrypted with the delegatee’s private key. We propose a type-and-identity-based proxy re-encryption scheme based on the Boneh-Franklin Identity Based Encryption (IBE) scheme. In our scheme, the delegator can categorize messages into different types and delegate the decryption right of each type to the delegatee through a proxy. Our scheme enables the delegator to provide the proxy fine-grained re-encryption capability. As an application, we propose a fine-grained Personal Health Record (PHR) disclosure scheme for healthcare service by applying the proposed scheme

On the Role of PKG for Proxy Re-encryption in Identity Based Setting

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\u27s public key into one that can be opened under Bob\u27s 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). Now CBE to IBE and IBE to IBE proxy re-encryption schemes are being standardized by IEEEP1363.3 working group. In this paper, based on we pay attention to the role of PKG for proxy re-encryption in identity based setting. We find that if we allow the PKG to use its master-key in the process of generating re-encryption key for proxy re-encryption in identity based setting, many open problems can be solved. Our main results are as following: We construct the first proxy re-encryption scheme from CBE to IBE which can resist malicious PKG attack, the first proxy re-encryption scheme from IBE to CBE, the second proxy re-encryption scheme based on a variant of BB_1 IBE, the first proxy re-encryption scheme based on BB_2 IBE, the first proxy re-encryption scheme based on SK IBE, we also prove their security in their corresponding security models

Non-Transferable Proxy Re-Encryption Scheme

SEC8: Selected topics in Information SecurityA proxy re-encryption (PRE) scheme allows a proxy to re-encrypt a ciphertext for Alice (delegator) to a ciphertext for Bob (delegatee) without seeing the underlying plaintext. However, existing PRE schemes generally suffer from at least one of the followings. Some schemes fail to provide the non-transferable property in which the proxy and the delegatee can collude to further delegate the decryption right to anyone. This is the main open problem left for PRE schemes. Other schemes assume the existence of a fully trusted private key generator (PKG) to generate the re-encryption key to be used by the proxy for re-encrypting a given ciphertext for a target delegatee. But this poses two problems in PRE schemes if the PKG is malicious: the PKG in their schemes may decrypt both original ciphertexts and re-encrypted ciphertexts (referred as the key escrow problem); and the PKG can generate reencryption key for arbitrary delegatees without permission from the delegator (we refer to it as the PKG despotism problem). In this paper, we propose the first non-transferable proxy re-encryption scheme which successfully achieves the nontransferable property. We show that the new scheme solved the PKG despotism problem and key escrow problem as well. © 2012 IEEE.published_or_final_versio

Improved Proxy Re-encryption Scheme for Symmetric Key Cryptography

A proxy re-encryption scheme can be executed by a semi-trusted proxy, so that we can transform a ciphertext encrypted with a key to another ciphertext encrypted with different key without allowing the proxy to access the plaintext. A method to implement a secure proxy re-encryption is by first converting the plaintext to an intermediate form by using an all or nothing transform (AONT). In this paper, we describe an improved proxy re-encryption scheme for symmetric cipher by advocating the usage of a variant of the AONT function in the proxy re-encryption scheme. We show that the scheme secure under Chosen Plaintext Attack (CPA) for all possible types of attackers

Cryptanalysis of a pairing-free certificate-based proxy re-encryption scheme for secure data sharing in public clouds

Proxy re-encryption(PRE) is a primitive that is used to facilitate secure access delegation in the cloud. Proxy re-encryption allows a proxy server to transform ciphertexts encrypted under one user\u27s public key to that under another user\u27s public key without learning anything about the underlying message or the secret key. Over the years proxy re-encryption schemes have been proposed in different settings. In this paper we restrict our analysis to certificate based proxy re-encryption. The first CCA secure certificate based PRE without bilinear pairings was proposed by Lu and Li in Future Generation Computer Systems, 2016. In this paper we present a concrete attack on their scheme and prove that it is not CCA secure

Sensors data collection framework using mobile identification with secure data sharing model

Sensors are the modules or electronic devices that are used to measure and get environmental events and send the captured data to other devices, usually computer processors allocated on the cloud. One of the most recent challenges is to protect and save the privacy issues of those sensors data on the cloud sharing. In this paper, sensors data collection framework is proposed using mobile identification and proxy re-encryption model for data sharing. The proposed framework includes: identity broker server, sensors managing and monitoring applications, messages queuing sever and data repository server. Finally, the experimental results show that the proposed proxy re-encryption model can work in real time

Proxy Re-Encryption in Blockchain-based Application

Nowadays, blockchain-based technology has risen to a new dimension. With the advantage of the decentralized identity, data are transferred through decentralized and public ledgers. Those new contracts provide great visibility. However, there is still a need to keep some data private in many cases. Those private data should be encrypted while still benefiting from the decentralized on-chain protocol. Securing those private data in such a decentralized blockchain-based system is thus a critical problem. Our solution provides a decentralized protocol that lets users grant access to their private data with proxy re-encryption in SpartanGold (a blockchain-based cryptocurrency). We implement a third-party storage provider called a proxy to store clients’ private data in an encrypted form. Whenever someone wants to access a client’s private data, the client uses their private key along with the buyer’s public key to generate a re-encryption key. The third-party proxy uses the re-encryption key to re-encrypt the client’s encrypted data for the recipient and send the result to the buyer. As a result, only the buyer can decrypt the re-encrypted data by using their private key, without revealing the data owner’s private key or the private data to the third-party proxy. Our protocol has secured the private data on the decentralized blockchain-based application without relying on trusted parties. We use medical data as a use case to validate our protocol. In our medical use case, the patient’s medical records are stored on the third-party proxy, and when specialists request medical data from the patient, the patient generates the re-encryption key and sends it to the proxy. The proxy re-encrypted the data and sends back to the specialists