What are the uses of blind signatures?

A blind signature is a type of digital signature in which the signer is blinded to the content of the message. The purpose behind this kind of signature is to maintain anonymity and hide confidential or secret information contained in the message.

How does blind signature work?

Let's suppose George wants to get John's signature on a message without revealing the content of the message to John. Following are the steps George will take :

1. Key generation: He will create a key pair (private key known only to him and public key known to both).

2. Message blinding: George will blind the message by encrypting it with an operation or random variable, such that John can't reverse it.

3. Sending the blinded message: The blinded message will be sent to John

4. Signature generation: John will apply his digital signature on the blinded message.

5. Unblinding the signature by George: On receiving the signed message, George will unblind it by reversing the operation he applied.

6. Signature verification: George will authenticate John's digital signature, using the public key.

Application of blind signature

The blind signature serves as a means for privacy, anonymity, unlinkability, and non-repudiation. Following are some of the applications for blind signatures.

Voting systems

Blind signatures can protect the privacy of the voters and prevent coercion. This way voters can obtain blind signatures on their ballots, allowing them to cast their votes without revealing which candidate they voted for.

Examples

Scytl, Voatz, and Smartmatic.

Digital cash systems

The users can withdraw electronic currency from the bank without revealing their account balance and bank statements. A blind signature will ensure that the bank cannot link the withdrawal request to the spender’s identity or track their transactions.

Examples

Mimblewimble-based projects, and Zcash (cryptocurrency).

Anonymous credentials

Blind signatures are used in systems that issue anonymous credentials. It can be used to allow users to verify specific qualifications and attributes, such as their age to prove that they are of legal age or level of education.

Examples

OpenMinded, Incognito and iden3

The above are just some of the many uses of blind signatures. To sum up, blind signatures are used where maintaining privacy, anonymity, and preventing traceability is critical.