Digital signatures represent one of the primary uses of public-key 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. In many aspects, digital signatures are equivalent to traditional handwritten signatures, but properly implemented digital signatures are more difficult to forge than the handwritten type. In order to verify a digital signature, the sender’s knowledge of the public key is required. Therefore, a key distribution mechanism is totally needed.
The most accepted approach is based on the usage of digital certificates, which enables the realization of the key exchange.