Calculate MD5 hash of an input string.
Hashing in general is defined as a transformation of a string of characters into a fixed-length key that represents the original string.
Special importance have the so called "one way" hashing algorithms.
"One way" hashing algorithms offer the feature that from a string we can get a hash key but from the hash key we can not find the original string.
So "one way" hashing algorithms can be used as digital signature for files or emails,
since the original file (string of characters) can be hashed (signed) into a key but from the known key we can not reproduce the original content.
(Message Digest 5) is a popular one-way hash function developed by Ronald Rivest which is used to create a message digest for digital signatures.
MD5 is faster than SHA-1, but is considered less secure.
MD5 is more secure from to the previous MD4. More info can be found at Wikipedia