SHA-1

Facebook has set the date: on September 30, the ancient and creaking SHA-1 hashing algorithm will make its tumbril trip and get the chop. SHA-1, designed by the NSA in 1995, is a one-way algorithm: a block of data is turned into a message digest. The digest can’t be turned back into the original message, but serves as a digital signature confirming the authenticity of (for example) the software you’ve downloaded....