digital code that can be attached to an electronically transmitted message
that uniquely identifies the sender. Like a written signature, the purpose
of a digital signature is to guarantee that the individual sending the
message really is who he or she claims to be.
Digital signatures are especially important for electronic commerce and
are a key component of most authentication schemes.
Digital Certificates facilitate the public key exchange that is required
to enable an SSL connection.
Digital certificate can be issued by any Certificate Authority, most web
browsers contain a list of trusted CAs, such as VeriSign or Thawte. Both
the client and server gets their digital certificates to authenticate