The signer's private key is then used to encrypt the message digest of signed document. A change to the document would result in a different digest and therefore a different signature. Therefore, knowing the digest has not changed is tantamount to knowing the message has not changed. The digital signature also verifies that the originator was indeed the sender of the message, because only the originator's public key could be used to decrypt the signature into the correct message digest of the document. Data and Key Recovery Reasons for data recovery may include an employee forgetting a password to unlock an encrypted file, the death of an employee who has encrypted some information, or someone attempting to hide criminal activity from law enforcement officials.
Key recovery is a particular form of data recovery.
With key recovery, a protected copy of the key is generally made available. The protection may involve a split key, where two organizations must both cooperate to decrypt the message. In contrast, data recovery generally refers to any alternative that provides a copy of the data to the authorized official. It is possible for certificates to vouch for a user's identity and also specify privileges the user has been granted. Privileges might include authority to view classified information or permission to modify material on a Web server among other privileges.