Paper 2003/148

A Tweakable Enciphering Mode

Shai Halevi and Phillip Rogaway


We describe a block-cipher mode of operation, CMC, that turns an n-bit block cipher into a tweakable enciphering scheme that acts on strings of mn bits, where m>=2. When the underlying block cipher is secure in the sense of a strong pseudorandom permutation (PRP), our scheme is secure in the sense of tweakable, strong PRP. Such an object can be used to encipher the sectors of a disk, in-place, offering security as good as can be obtained in this setting. CMC makes a pass of CBC encryption, xors in a mask, and then makes a pass of CBC decryption; no universal hashing, nor any other non-trivial operation beyond the block-cipher calls, is employed. Besides proving the security of CMC we initiate a more general investigation of tweakable enciphering schemes, considering issues like the non-malleability of these objects.

Available format(s)
Secret-key cryptography
Publication info
Published elsewhere. CRYPTO'03, LNCS, vol. 2729, Springer-Verlag, 2003
Block-cipher usagecryptographic standardsdisk encryptionmodes of operationprovable securitysector-level encryptionsymmetric encryption.
Contact author(s)
shaih @ watson ibm com
2003-07-28: received
Short URL
Creative Commons Attribution


      author = {Shai Halevi and Phillip Rogaway},
      title = {A Tweakable Enciphering Mode},
      howpublished = {Cryptology ePrint Archive, Paper 2003/148},
      year = {2003},
      note = {\url{}},
      url = {}
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