Anonymous credential systems are related to the concept of untraceable or anonymous payments. In this important work, Chaum presents a new cryptographic primitive, blind signature protocols. In such a scheme the signer neither learns the message he signs, nor the signature the recipient obtains for his message. Blind signatures are an important building block of many privacy-sensitive applications, such as anonymous payments, voting, and credentials. The original idea for an anonymous credential system was derived from blind signatures, but relied on a trusted party for credential transfer—the translation from one pseudonym to another. The blind signature scheme introduced by Chaum was based on RSA signatures and based on the discrete logarithm problem can be used for constructing anonymous credential systems.