HCTR: A Variable-Input-Length Enciphering Mode

This paper proposes a blockcipher mode of operation, HCTR, which is a length-preserving encryption mode. HCTR turns an n-bit blockcipher into a tweakable blockcipher that supports arbitrary variable input length which is no less than n bits. The tweak length of HCTR is fixed and can be zero. We prove that HCTR is a strong tweakable pseudorandom permutation (sprp), when the underlying blockcipher is a strong pseudorandom permutation (sprp). HCTR is shown to be a very efficient mode of operation when some pre-computations are taken into consideration. Arbitrary variable input length brings much flexibility in various application environments. HCTR can be used in disk sector encryption, and other length-preserving encryptions, especially for the message that is not multiple of n bits.

• Type: Conference
• Year: 2005
• Where: CISC
• Authors: Peng Wang, Dengguo Feng, Wenling Wu
• Keywords: Arbitrary Variable Input, CISC 2005, Pseudorandom Permutation, Variable Input Length