2001 | OriginalPaper | Chapter
Cryptanalysis of the “Augmented Family of Cryptographic Parity Circuits” Proposed at ISW’97
Author : A. M. Youssef
Published in: Selected Areas in Cryptography
Publisher: Springer Berlin Heidelberg
Included in: Professional Book Archive
Activate our intelligent search to find suitable subject content or patents.
Select sections of text to find matching patents with Artificial Intelligence. powered by
Select sections of text to find additional relevant content using AI-assisted search. powered by
At Crypto’90, Koyama and Terada proposed a family of cryptographic functions for application to symmetric block ciphers. Youssef and Tavares showed that this family is affine and hence it is completely insecure. In response to this, Koyama and Terada modified their design, by including a data dependent operation between layers. The modified family of circuits was presented in the first international security workshop (ISW’97). In this paper, we show that the modified circuit can be easily broken by a differential-like attack. More explicitly, we show that after d rounds, and for any specific key K, the input space can be partitioned into M ≤ 2d sets such that the ciphertext Y of each set is related to the plaintext X by an affine relation. The expected value of M ≪ 2d. Our attack enables us to explicitly recover these linear relations. We were able to break an 8—round 64—bit version of this family in few minutes on a workstation using less than 220 chosen plaintext-ciphertext pairs.