Cryptology ePrint Archive: Report 2000/039
Encryption Modes with Almost Free Message Integrity
Charanjit S. Jutla
Abstract: We define a new mode of operation for block encryption which in
addition to assuring confidentiality also assures message integrity.
In contrast, previously for message integrity a separate pass was
required to compute a cryptographic message authentication code (MAC).
The new mode of operation, called Integrity Aware CBC (IACBC),
requires a total of m + log m block encryptions on a plaintext of
length m blocks. The well known CBC (cipher block chaining) mode
requires m block encryptions. The second pass of computing the MAC
essentially requires additional m block encryptions. We also show a
lower bound of \Omega(log m) additional block encryptions for any
reasonably modeled (linear) scheme which assures message integrity
along with confidentiality.
Category / Keywords: secret-key cryptography / Block cipher, CBC, authentication, MAC, modes of operation
Date: received 1 Aug 2000
Contact author: csjutla at watson ibm com
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Version: 20000801:174658 (All versions of this report)
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