Volume 11 - Issue 2
A Provably Secure Conditional Proxy Re-Encryption Scheme without Pairing
- Arinjita Paul
Department of Computer Science and Engineering, IIT Madras, Chennai, India
arinjita@cse.iitm.ac.in
- S. Sharmila Deva Selvi
Department of Computer Science and Engineering, IIT Madras, Chennai, India
sharmila@cse.iitm.ac.in
- Pandu Rangan
Department of Computer Science and Engineering, IIT Madras, Chennai, India
prangan@cse.iitm.ac.in
Keywords: Proxy Re-Encryption, Public Key, Conditional, Pairing-less, Unidirectional, Single hop, CCA-secure
Abstract
Blaze, Bleumer and Strauss introduced the notion of proxy re-encryption (PRE), a cryptographic
primitive that enables a semi-trusted proxy to transform ciphertexts under the public key of a user
(delegator) into ciphertexts under the public key of another user (delegatee). The important property
to note here is, the proxy should not learn anything about the plaintext encrypted. In 2009, Weng
et al: introduced the concept of conditional proxy re-encryption (CPRE), which permits the proxy to
re-encrypt only ciphertexts satisfying a condition specified by the delegator into a ciphertext for the
delegatee. CPRE enables fine-grained delegation of decryption rights useful in many practical scenarios,
such as blockchain-enabled distributed cloud storage and encrypted email forwarding. Several
CPRE schemes exist in the literature based on costly bilinear pairing operation in the random oracle
model. We propose the first construction of an efficient CPRE scheme without pairing, satisfying
chosen ciphertext security under the computational Diffie Hellman (CDH) assumption and its variant
in the random oracle model.