Elastic Block Ciphers in Practice: Constructions and Modes of Encryption
We demonstrate the general applicability of the elastic block cipher method by constructing examples from existing block ciphers: AES, Camellia, MISTY1 and RC6. An elastic block cipher is a variable-length block cipher created from an existing fixed-length block cipher. The elastic version supports any block size between one and two times that of the original block size. We compare the performance of the elastic versions to that of the original versions and evaluate the elastic versions using statistical tests measuring the randomness of the ciphertext. The benefit, in terms of an increased rate of encryption, of using an elastic block cipher varies based on the specific block cipher and implementation. In most cases, there is an advantage to using an elastic block cipher to encrypt blocks that are a few bytes longer than the original block length. The statistical test results indicate no obvious flaws in the method for constructing elastic block ciphers. We also use our examples to demonstrate the concept of a generic key schedule for block ciphers. In addition, we present ideas for new modes of encryption using the elastic block cipher construction.
KeywordsBlock Size Block Cipher Advance Encryption Standard Performance Benefit Round Function
Unable to display preview. Download preview PDF.
- K. Aoki, T. Ichikawa, M. Kanda, M. Matsui, S. Moriai, J. Nakajima, and T. Tokita. “Camellia: A 128-Bit Block Cipher Suitable for Multiple Platforms – Design and Analysis”. In Proceedings of Selected Areas in Cryptography, LNCS 2012, Springer-Verlag, pp. 39–56, 2000.Google Scholar
- M. Bellare and P. Rogaway. “On the Construction of Variable Length-Input Ciphers”. In Proceedings of Fast Software Encryption, LNCS 1636, Springer-Verlag, 1999.Google Scholar
- M. Ciet, G. Piret, and J. Quisquater. “Related-Key and Slide Attacks: Analysis, Connections and Improvements, Extended Abstract”. UCL Crypto Group Technical Report, 2002.Google Scholar
- D. Cook. “Elastic Block Ciphers”. Ph.D. Thesis, Columbia University, New York, 2006.Google Scholar
- D. Cook, M. Yung, and A. Keromytis. “Elastic Block Ciphers: The Basic Design”. In Proceedings of ASIACCS, ACM, pp. 350–355, March 2007.Google Scholar
- J. Daemon and V. Rijmen, “The Design of Rijndael: AES the Advanced Encryption Standard”. Springer-Verlag, Berlin, 2002.Google Scholar
- A. Joux, G. Martinet, and F.Valette. “Blockwise-Adaptive Attackers: Revisiting the (In)Security of Some Provably Secure Encryption Models”. In Proceedings of Advances in Cryptology – CRYPTO, LNCS 2442, Springer-Verlag, August 2002.Google Scholar
- M. Matsui, “New Block Encryption Algorithm MISTY”. In Proceedings of Fast Software Encryption, LNCS 1267, Springer-Verlag, pp. 54–68, 1997.Google Scholar
- I. Mironov. “(Not So) Random Shuffles of RC4”. In Proceedings of Advances in Cryptology – CRYPTO, LNCS 2442, Springer-Verlag, August 2002.Google Scholar
- “NESSIE Security Report, Version 2”. https://www.cosic.esat.kuleuven.ac.be/nessie, February 2003.
- NIST. “Randomness Testing of the Advanced Encryption Standard Finalist Candidates”, http://citeseer.ist.psu.edu/soto00randomness.html, March 2000.
- NIST. “A Statistical Test Suite for Random and Pseudorandom Number Generators for Cryptographic Applications”. NIST Special Publication 800–22. http://www.csrc.nist.gov/publications/nistir, 2001.
- NIST. “FIPS 197 Advanced Encryption Standard (AES)”, http://www.csrc.nist.gov/publications/fips/ fips197/fips-197.pdf, 2001.
- NIST. “FIPS 180-2 Secure Hash Standard”, http://www.csrc.nist.gov/publications/fips/fips180-2/fips180-2withchangenotice.pdf, 2002.
- S. Patel, Z. Ramzan, and G. Sundaram. “Efficient Constructions of Variable-Input-Length Block Ciphers”. In Proceedings of Selected Areas in Cryptography, LNCS 3357, Springer-Verlag, 2004.Google Scholar
- random.org. http://wwww.random.org/files.
- R. Rivest. “RC4”. In Applied Cryptography by B. Schneier, John Wiley and Sons, New York, 1996.Google Scholar
- R. Rivest, M.J.B. Robshaw, R. Sidney, and Y.L. Yin. “RC6 Block Cipher”. http://www.rsa.security.com/rsalabs/rc6, 1998.