In cryptography a blind signature as introduced by David Chaum
is a form of digital signature in which the content of a message
is disguised (blinded) before it is signed. The resulting blind
signature can be publicly verified against the original,
unblinded message in the manner of a regular digital signature.
Blind signatures are typically employed in privacy-related
protocols where the signer and message author are different
parties. Examples include cryptographic election systems and
digital cash schemes. An often-used analogy to the cryptographic
blind signature is the physical act of enclosing a ballot in a
special carbon paper lined envelope. The ballot can be marked
through the envelope by the carbon paper. It is then sealed by
the voter and handed to an official which signs the envelope.
Once signed, the package can be given back to the voter, who
transfers the now signed ballot to a new unmarked normal
envelope. Thus, the signer does not view the message content,
but a third party can later verify t