Cryptanalysis of Skipjack Reduced to 31 Rounds Using Impossible Differentials

Abstract. The boomerang attack and the rectangle attack are two attacks that utilize differential cryptanalysis in a larger construction. Both attacks treat the cipher as a cascade of two sub-ciphers, where there exists a good differential for each sub-cipher, but not for the entire cipher. In this paper we combine the boomerang (and the rectangle) attack with related-key differentials.The new combination is applicable to many ciphers, and we demonstrate its strength by introducing attacks on reduced-round versions of AES and IDEA. The attack on 192-bit key 9-round AES uses 256 different related keys. The 6.5-round attack on IDEA uses four related keys (and has time complexity of 2 88.1 encryptions). We also apply these techniques to COCONUT98 to obtain a distinguisher that requires only four related-key adaptive chosen plaintexts and ciphertexts. For these ciphers, our results attack larger number of rounds or have smaller complexities then all previously known attacks.

show abstract

“…is high enough (or zero [3]). The common assumption is that this probability is quite uniform over all keys and plaintexts.…”

Section: Related-key Boomerang and Rectangle Attacksmentioning

confidence: 99%

“…Otherwise, as (z, 0) → (z, 0) we get a related-key impossible differential (due to the miss in the middle attack [3,2]). …”

Section: Related-key Boomerang Distinguisher For Coconut98mentioning

confidence: 99%

Related-Key Boomerang and Rectangle Attacks

Biham

Dunkelman

Keller

2005

Lecture Notes in Computer Science

Self Cite

155

View full text Add to dashboard Cite

show abstract

“…In 2002, Moon et al [19] presented an impossible differential [2,14] attack on 14 rounds of XTEA. In 2003, Hong et al [6] presented a differential [5] attack on 15 rounds of XTEA and a truncated differential [13] attack on 23 rounds of XTEA, where the former attack is due to a 13-round differential with probability 2 −54.795 and the latter attack is due to a 8-round truncated differential.…”

Section: Introductionmentioning

confidence: 99%

Related-key rectangle attack on 36 rounds of the XTEA block cipher

2008

Int. J. Inf. Secur.

View full text Add to dashboard Cite

XTEA is a 64-round block cipher with a 64-bit block size and a 128-bit user key, which was designed as a short C program that would run safely on most computers. In this paper, we present a related-key rectangle attack on a series of inner 36 rounds of XTEA without making a weak key assumption, and a related-key rectangle attack on the first 36 rounds of XTEA under certain weak key assumptions. These are better than any previously published cryptanalytic results on XTEA in terms of the numbers of attacked rounds.

show abstract

“…is high enough (or zero [5]). A related-key differential is a triplet of a plaintext difference ∆P , a ciphertext difference ∆C, and a key difference ∆K, such that…”

Section: Related-key Differentialsmentioning

confidence: 99%

A Related-Key Rectangle Attack on the Full KASUMI

Biham

Dunkelman

Keller

2005

Lecture Notes in Computer Science

Self Cite

View full text Add to dashboard Cite

Abstract. KASUMI is an 8-round Feistel block cipher used in the confidentiality and the integrity algorithms of the 3GPP mobile communications. As more and more 3GPP networks are being deployed, more and more users use KASUMI to protect their privacy. Previously known attacks on KASUMI can break up to 6 out of the 8 rounds faster than exhaustive key search, and no attacks on the full KASUMI have been published.In this paper we apply the recently introduced related-key boomerang and rectangle attacks to KASUMI, resulting in an attack that is faster than exhaustive search against the full cipher. We also present a relatedkey boomerang distinguisher for 6-round KASUMI using only 768 adaptively chosen plaintexts and ciphertexts encrypted or decrypted under four related keys.Recently, it was shown that the security of the entire encryption system of the 3GPP networks cannot be proven using only the "ordinary" assumption that the underlying cipher (KASUMI) is a Pseudo-Random Permutation. It was also shown that if we assume that KASUMI is also secure with respect to differential-based related-key attacks then the security of the entire system can be proven. Our results show that theoretically, KASUMI is not secure with respect to differential-based relatedkey attacks, and thus, the security of the entire encryption system of the 3GPP cannot be proven at this time.

show abstract

Cryptanalysis of Skipjack Reduced to 31 Rounds Using Impossible Differentials

Cited by 198 publications

References 15 publications

Related-Key Boomerang and Rectangle Attacks

Related-Key Boomerang and Rectangle Attacks

Related-key rectangle attack on 36 rounds of the XTEA block cipher

A Related-Key Rectangle Attack on the Full KASUMI

Contact Info

Product

Resources

About