Now that we've covered hashing, it's time to go over a related concept: digital signatures. Digital signatures use the properties of hashing to not only prove that data hasn't changed but to provide assurances of who created it. Digital signatures work off the concept of hashing but add a new concept as well: digital keys.
All common approaches to digital signatures use what is called Public Key Cryptography. In Public Key Cryptography, there are two keys: one public and one private. To create a signature, the first hash is produced of the original data, and then the private key is used to encrypt that hash. That encrypted hash, along with other information, such as the encryption method used to become part of the signature, are attached to the original data.
This is where the public key comes into play. The mathematical link between the public key and the private key allows the public key to decrypt the hash, and then the hash can be used to check...