Authors:
Chuan-Wen Loe
and
Khoongming Khoo
Affiliation:
DSO National Laboratories, Singapore
Keyword(s):
Cipher Block Chaining, Adaptive Chosen Plaintext Attack, Input-Output Masked CBC.
Related
Ontology
Subjects/Areas/Topics:
Ipsec, Vpns and Encryption Modes
Abstract:
In the literature, several encryption modes of operation based on cipher block chaining (CBC) has been proven
to be secure under non-adaptive chosen plaintext attack (CPA-1) in the left-or-right (LOR) or find-then-guess
(FTG) security models. However, it was shown by Joux et. al. at Crypto 2002 that if we allow the adversary
to perform an adaptive chosen plaintext attack (CPA-2), then CBC, ABC and GEM are susceptible to FTG attacks. In this paper, we propose a new CBC-type encryption called input-output masked CBC (IO-CBC) which can protect against FTG and LOR attacks based on forcing an input collision, protects against Joux’s FTG attack under proper implementation, and increases the difficulty of linear and differential cryptanalysis. The efficiency of IO-CBC is comparable to CBC because it does only one additonal encryption when compared with CBC. We also reasoned that the security proof of an IO-CBC variant follows from that of OCB.