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To improve the network security by a cryptographic primitive called proxy re-encryption in which a proxy can transform a ciphertext encrypted under one key without seeing the actual plaintext into an encryption of the same plaintext under another key. This cryptographic concept has recently drawn renewed interest. Some researchers also showed how to properly define chosen-ciphertext security for the primitive. This system supports bidirectional as the translation key allows converting ciphertexts in both directions. The proposed concept presents the unidirectional proxy re-encryption schemes with chosen-ciphertext security without using the random oracle idealization. In 2008, Libert and Vergnaud presented the first construction of unidirectional proxy re-encryption scheme with chosen-ciphertext security in the standard model. The limitation of their scheme is the longer length of original ciphertext and re-encrypted ciphertext. In this paper, an improvement is performed in Libert and Vergnaud scheme by improving the security levels of encryption using ASCII values. The proposed work additionally outlines Non-Transitive Unidirectional Proxy Re-Encryption (PRE) schemes. This paper justifies the strength of this PRE with experimental results.
Date of Conference: 13-14 Dec. 2012