A digital signature or
digital signature scheme is a type of asymmetric cryptography.
For messages sent through an insecure channel, a properly
implemented digital signature gives the receiver reason to believe
the message was sent by the claimed sender. Digital signatures are
equivalent to traditional handwritten signatures in many respects;
properly implemented digital signatures are more difficult to forge
than the handwritten type. Digital signature schemes in the sense
used here are cryptographically based, and must be implemented
properly to be effective.