In some cases, cryptographic hashes will be keyed in much the same way that encryption functions are. If so, only someone who possesses the key can verify the hash's accuracy. In practical terms, it is generally possible to create a keyed hash function by simply prepending or appending a key onto the message M prior to hashing it (that is, 'H(k+M)'). However, some keyed hashes utilize a key value in a more deeply integrated way within the algorithm.