Cryptology ePrint Archive: Report 2008/401
Two New Efficient CCA-Secure Online Ciphers: MHCBC and MCBC
Abstract: Online ciphers are those ciphers whose ciphertexts can be computed
in real time by using a length-preserving encryption algorithm.
HCBC1 and HCBC2 are two known examples of Hash Cipher Block
Chaining online ciphers. The first construction is secure against
chosen plaintext adversary (or called CPA-secure) whereas the
latter is secure against chosen ciphertext adversary (or called
CCA-secure). In this paper, we have provided simple security
analysis of these online ciphers. We have also proposed two new
more efficient chosen ciphertext secure online ciphers
modified-HCBC (MHCBC) and modified-CBC (MCBC). If one uses a
finite field multiplication based universal hash function, the
former needs one less key and one less field multiplication
compared to HCBC2. The MCBC does not need any universal hash
function and it needs only one blockcipher key unlike the other
three online ciphers where two independent keys (hash function and
blockcipher) are required.
Category / Keywords: secret-key cryptography / online cipher, CBC, universal hash function, random permutation.
Publication Info: A preliminary version of this paper appears in Advances in Cryptology - INDOCRYPT 2008, Lecture Notes in Computer Science Vol. ???, pp. ???, Springer-Verlag, 2008.
Date: received 20 Sep 2008
Contact author: mridul nandi at gmail com
Available format(s): PDF | BibTeX Citation
Version: 20080924:032146 (All versions of this report)
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