ALGEBRAIC DEGREE ESTIMATION OF BLOCK CIPHERS USING RANDOMIZED ALGORITHM; UPPER-BOUND INTEGRAL DISTINGUISHER.
ALGEBRAIC DEGREE ESTIMATION OF BLOCK
CIPHERS USING RANDOMIZED ALGORITHM;
UPPER-BOUND INTEGRAL DISTINGUISHER.
Haruhisa Kosuge and Hidema Tanaka
National Defense Academy of Japan, Yokosuka, Japan
ABSTRACT
Integral attack is a powerful method to recover the secret key of block cipher by exploiting a characteristic
that a set of outputs after several rounds encryption has ( integral distinguisher). Recently, Todo proposed a
new algorithm to construct integral distinguisher with division property. However, the existence of integral
distinguisher which holds in additional rounds can not be denied by the algorithm. On the contrary, we
take an approach to obtain the number of rounds which integral distinguisher does not hold ( upper-bound
integral distinguisher). The approach is based on algebraic degree estimation. We execute a random search
for a term which has a degree equals the number of all inputted variables. We propose an algorithm and
apply it to PRESENT and RECTANGLE. Then, we confirm that there exists no 8-round integral distinguisher
in PRESENT and no 9-round integral distinguisher in RECTANGLE. From the facts, integral attack for more
than 11-round and 13-round of PRESENT and RECTANGLE is infeasible, respectively.
KEYWORDS
Chosen plaintext attack, Integral attack, Algebraic normal form, Algebraic degree, PRESENT, RECTANGLE
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