CHOSEN-KEY ATTACKS ON A BLOCK CIPHER
Robert S. Winternitz, Martin E. Hellman · Cryptologia · 1987
This paper presents a new attack on a block cipher, which is stronger than all previously considered attacks. This “chosen-key attack” is a generalization of the well accepted chosen-text attack. We give an example of a block cipher which is strong under a chosen-text attack, but immediately vulnerable to a chosen-key attack. A general chosen-key attack breaks an n bit key cipher in 2 n/2 operations. A black-box argument shows that this is the best possible for general attacks.