Digital Signature

   Digital signature is a method of mathematically (with [1]cryptographical
   algorithms) proving that, with a very high probability, a digital message
   or document has been produced by a specific sender, i.e. it is something
   aka traditional signature which gives a "proof" that something has been
   written by a specific individual.

   It works on the basis of [2]asymmetric cryptography: the signature of a
   message is a pair of a public key and a number (the signature) which can
   only have been produced by the owner of the private key associated with
   the public key. This signature is dependent on the message data itself,
   i.e. if the message is modified, the signature will no longer be valid,
   preventing anyone who doesn't posses the private key from modifying the
   message. The signature number can for example be a [3]hash of the message
   decoded with the private key -- anyone can check that the signature
   encoded with the public key gives the document hash, proving that whoever
   computed the signature number must have possessed the private key.

   Signatures can be computed e.g. with the [4]RSA algorithm.

   The advantage here is that [5]anonymity can be kept with digital
   signatures; no private information such as the signer's real name is
   required to be revealed, only his public key. Someone may ask why we then
   even sign documents if we don't know by whom it is signed lol? But of
   course the answer is obvious: many times we don't need to know the
   identity of the signer, we just need to know that different messages have
   all been written by the same man, and this is what a digital signature can
   ensure. And of course, if we want, a public key can have a real identity
   assigned if desirable, it's just that it's not required.

See Also

     * [6]tripcode

Links:
1. cryptography.md
2. asymmetric_cryptography.md
3. hash.md
4. rsa.md
5. anonymity.md
6. tripcode.md