Cryptanalysis of the Stream Cipher ABC v2
Hongjun Wu, Bart Preneel · Lirias · 2006
Abstract. ABC v2 is a software-efficient stream cipher with 128-bit key. In this paper, we apply a fast correlation attack to break ABC v2 with weak keys. There are about 2 96 weak keys in ABC v2. The complexity to identify a weak key and to recover the internal state of a weak key is low. Identifying a weak key from 2 32 random keys requires 6460 keystream bytes and 2 13.5 operations for each key. Recovering the internal state of a weak key requires about 2 19.5 keystream bytes and 2 32.84 operations. A similar attack can be applied to break ABC v1 with much lower complexity than the previous attack on ABC v1. Keywords. Fast correlation attack, key-dependent S-box, stream cipher, ABC v2. 1