A blind signature scheme is a type of digital signature that conceals the identity of the message contents and the sender.
In these schemes the sender’s message is concealed — or blinded — prior to the recipient signing it. Blind signature schemes are useful in applications where information on the sender is an important feature of the communication.
Electronic voting is a real-world example of a blind signature scheme is a properly functioning electronic voting system. In this example, the sender (voter) and the signer (recipient, voting authority) are unrelated and the sender’s personal privacy and voting preference are paramount. The signature is considered valid enough to warrant the vote being recorded with confidence and the voter remains anonymous.
Going further, should the voting authority be called upon to validate the information they received they are able to validate the message’s authenticity but unable to connect it with the sender (called unlinkability).
"Digital currency transactions on the blockchain use a blind signature scheme so that the sender and transaction detail are secure and untraceable."