New Insights on Impossible Differential Cryptanalysis
Since its introduction, impossible differential cryptanalysis has been applied to many ciphers. Besides the specific application of the technique in various instances, there are some very basic results which apply to generic structures of ciphers, e.g., the well known 5-round impossible differential of Feistel ciphers with bijective round functions.
In this paper we present a new approach for the construction and the usage of impossible differentials for Generalized Feistel structures. The results allow to extend some of the previous impossible differentials by one round (or more), answer an open problem about the ability to perform this kind of analysis, and tackle, for the first time the case of non-bijective round functions.
KeywordsImpossible differential cryptanalysis Miss in the middle Generalized Feistel Matrix method
- 1.Adams, C., Heys, H., Tavares, S., Wiener, M.: The CAST-256 Encryption Algorithm (1998); AES Submission Google Scholar
- 6.Burwick, C., Coppersmith, D., D’Avignon, E., Gennaro, R., Halevi, S., Jutla, C., Matyas Jr., S.M., O’Connor, L., Peyravian, M., Safford, D., Zunic, N.: MARS - a candidate cipher for AES (1998); AES submissionGoogle Scholar
- 8.Daemen, J., Rijmen, V.: AES Proposal: Rijndael (1998); NIST AES proposalGoogle Scholar
- 9.Keliher, L., Sui, J.: Exact Maximum Expected Differential and Linear Probability for 2-Round Advanced Encryption Standard (AES) (2005); IACR ePrint report 2005/321Google Scholar
- 12.Knudsen, L.R.: Deal — A 128-bit Block Cipher (1998); AES submissionGoogle Scholar
- 13.Luo, Y., Wu, Z., Lai, X., Gong, G.: A Unified Method for Finding Impossible Differentials of Block Cipher Structures (2009); IACR ePrint report 2009/627Google Scholar
- 16.Pudovkina, M.: On Impossible Truncated Differentials of Generalized Feistel and Skipjack Ciphers. Presented at the Rump Session of the FSE 2009 Workshop (2009), http://fse2009rump.cr.yp.to/e31bba5d1227eac5ef0daa6bcbf66f27.pdf
- 17.Rivest, R.L., Robshaw, M.J., Sidney, R., Yin, Y.L.: The RC6 Block Cipher (1998); AES submissionGoogle Scholar
- 18.US Government: SKIPJACK and KEA Algorithm Specification (1998)Google Scholar
- 19.US National Institute of Standards and Technology: Advanced Encryption Standard (2001); Federal Information Processing Standards Publications No. 197Google Scholar