Advanced Infrastructure Penetration Testing

Hash functions and message integrity

Hash functions are mathematical  functions that take an arbitrarily sized input string, and generate a fixed-size output called a hash value or a message digest. A good hash function should calculate hashes easily; it will be very difficult to calculate the plaintexts of a given hash, and it does not generate the same hash for two different inputs, except in rare cases.

There are many well-known hash functions used nowadays; they are as follows:

• Hashed message authentication code
• Message Digest (MD2)
• Message Digest (MD4)
• Message Digest (MD5), if you want to encrypt or decrypt a plaintext you can use