[Encrypt_MD5] generates a 128 bit hash value for a string. Accepts one parameter, a string to be encrypted.

The MD5 hash value is a 128 bit string that identifies the input string. This is a one way operation. There is no way to 'decrypt' the hash value back into the input string.

Passwords can be stored by generating an MD5 hash value for each password and storing it instead of the plaintext password. In order to validate a password, the input from the site visitor is also used to generate an MD5 hash value and then the new hash value is compared to the stored hash value. If they match, the password given was the same as the password which is being stored.