The blind signature is the oldest and most consequential trick in privacy cryptography, yet most people who benefit from it daily have never seen how it works. This post traces the full family tree: Chaum's RSA construction, Wagner's elliptic curve variant, Schnorr blinding and the attack that nearly killed it, BLS threshold signatures, and the algebraic MACs that replaced them all. Each scheme gets an intuitive walkthrough showing why it works and which real systems chose which construction.