Blind signatures are a cryptographic technique that allows one party to sign a message without knowing its content. This is achieved by "blinding" the message, which means transforming it in a way that hides its information. The signer then produces a signature on this blinded message, which can later be verified by anyone without revealing the original message. This method is often used in privacy-preserving applications, such as electronic voting and digital cash systems. By ensuring that the signer cannot link their signature to the original message, blind signatures help maintain the anonymity of the user while still providing proof of authenticity.