Advances in Hash Function Cryptanalysis

When significant weaknesses are found in cryptographic primitives on which the everyday security of the Internet relies, it is important that they are replaced by more secure alternatives, even if the weaknesses are only theoretical. This is clearly emphasized by our construction of a (purposely crippled) rogue Certification Authority (CA) in 2009 that in principle enabled the impersonation of all secure websites. This was possible due to the continued use of the insecure cryptographic hash function MD5 by a leading commercial CA. The hash function SHA-1, the successor to MD5 as the de facto hash function standard, has been theoretically broken since 2005. The Cryptology group at CWI has recently made a significant step towards a practical attack on SHA-1 that has long been anticipated, as well as efficient counter-measures against these cryptographic attacks.