ÿþ MD4, MD5 and SHA-1 Algorithms form input {font-family: "Courier New", Verdana; font-size:11pt;} MD4, MD5 ŒT SHA-1 —{Õl The MD4, MD5 and SHA-1 algorithms are secure hash functions. They take a string input, and produce a fixed size number - 128 bits for MD4 and MD5; 160 bits for SHA-1. This number is a hash of the input - a small change in the input results in a substantial change in the output. The functions are thought to be secure, in the sense that it would require an enormous amount of computing power to find a string which hashes to a chosen value.         'Yë[W[Ík