Blind Signatures

A blind signature, invented by David Chaum, is a form of digital signature in which the contents of a message are hidden before it is signed, ensuring that the signer cannot see the message’s content. This is done by disguising the message’s content or “blinding” it before it’s signed. The resulting blind signature can be publicly verified against the original, unblinded message, just like a regular digital signature.

There are a few different use cases for blind signatures. One use case for blind signatures is eCash. Blind signatures ensure that a payment system can verify transactions without knowing the details of the transaction, preserving user privacy. Another prominent use case for blind signatures could be for voting systems. This would allow a vote to be signed or verified by an authority without revealing the voter’s choice, ensuring the vote is legitimate.

For example, let’s say that Alice wants to make a digital vote in an election. Alice would make her vote and then apply a blinding factor to her vote (or message). This means that Bob would not be able to see the content or choice of Alice’s vote. Bob may be able to see other information about Alice. For example, Bob may be able to verify Alice’s identity to make sure that she doesn’t vote more than once. Once Bob has verified her identity and other information, he would sign the vote from Alice, authenticating it. Alice could then remove the blinding factor from the signed message, revealing Bob’s signature on her vote showing that it’s authenticated before finally submitting her vote to the election.