Paper 2004/141

Elastic AES

Debra L. Cook, Moti Yung, and Angelos D. Keromytis


Recently an algorithmic schema was proposed for converting any existing block cipher into one which excepts variable length inputs with the computational workload increasing in proportion to the block size. The resulting cipher is referred to as an elastic block cipher. The initial work presented immunity to certain key recovery attacks, and left open further analysis of the method and its possible instantiations. In order to provide a concrete example of an elastic block cipher, we design and implement an elastic version of the Advanced Encryption Standard (AES) cipher which accepts all block sizes in the range 128 to 255 bits. To validate the design we perform differential cryptanalysis on elastic AES which confirms that the cipher does not introduce potential differential attacks as a result of a subset of bits being omitted from each round (which is at the heart of the elastic design). We also compare the performance of software implementations of elastic AES and regular AES on variable size inputs, as a step in determining the practicality of the elastic version.

Available format(s)
Secret-key cryptography
Publication info
Published elsewhere. Unknown where it was published
variable length block ciphersblock cipher design
Contact author(s)
dcook @ cs columbia edu
2004-07-06: revised
2004-06-16: received
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Creative Commons Attribution


      author = {Debra L.  Cook and Moti Yung and Angelos D.  Keromytis},
      title = {Elastic AES},
      howpublished = {Cryptology ePrint Archive, Paper 2004/141},
      year = {2004},
      note = {\url{}},
      url = {}
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