We demonstrate an active attack on the WEP protocol that is able to recover a 104-bit WEP key using less than 40.000 frames with a success probability of 50%. In order to succeed in 95% of all cases, 85.000 packets are needed. The IV of these packets can be randomly chosen. This is an improvement in the number of required frames by more than an order of magnitude over the best known key-recovery attacks for WEP. On a IEEE 802.11g network, the number of frames required can be obtained by re-injection in less than a minute. The required computational effort is approximately 2 20 RC4 key setups, which on current desktop and laptop CPUs is neglegible. 1 the ICV being a CRC32 checksum, it does not provide integrity in the cryptographical sense. The ICV rather is another layer of protection against accidental data corruption.

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Abstract. We construct and analyze Feistel and SPN ciphers that have a sound design strategy against linear and differential attacks but for which the encryption process can be described by very simple polynomial equations. For a block and key size of 128 bits, we present ciphers for which practical Gröbner basis attacks can recover the full cipher key requiring only a minimal number of plaintext/ciphertext pairs. We show how Gröbner bases for a subset of these ciphers can be constructed with neglegible computational effort. This reduces the key-recovery problem to a Gröbner basis conversion problem. By bounding the running time of a Gröbner basis conversion algorithm, FGLM, we demonstrate the existence of block ciphers resistant against differential and linear cryptanalysis but vulnerable against Gröbner basis attacks.

Abstract. We demonstrate an efficient method for computing a Gröbner basis of a zero-dimensional ideal describing the key-recovery problem from a single plaintext/ciphertext pair for the full AES-128. This Gröbner basis is relative to a degree-lexicographical order. We investigate whether the existence of this Gröbner basis has any security implications for the AES.