MD5 and SHA-1 are widely used in cryptography to generate one-way hashes of data. SHA-1 is a more secure version of the earlier SHA-0 algorithm.
Antoine Joux, a French cryptography researcher, demonstrated a technique to reduce the complexity of attacking SHA-0 by many orders of magnitude. While considerable computing power is still required to conduct such an attack, the barrier for an attacker is much lower. Joux demonstrated a way to find a collision – identical data producing the same hash – which could be used to attack encrypted data.
At the same time, a similar attack against SHA-1 has been described. And Chinese researchers published a paper describing an attack against the MD5 algorithm. Although an initial study was found to be flawed, the techniques were sound and have been independently verified.
This comes as the National Institute of Standards and Technology (NIST) has recommended that federal departments abandon DES encryption as modern computing may render it ineffective.