An earlier open source implementation of the identity metasystem conceived by Microsoft and embodied in Microsoft's CardSpace. Unlike the Windows-only CardSpace, Higgins supported other operating systems.
Enhanced Information Cards
Higgins provided enhanced personal and managed cards. Information cards created in CardSpace could be used in Higgins, but the "z-cards" and "r-cards" created in Higgins were not supported in CardSpace. Both systems were in their embryonic stages, and changes in compatibility were expected as this high-level identity architecture caught on in the late 2000s, but it never did.
The z-card added functionality to the managed card (m-card). It offered more privacy by caching the security token locally, and it supported subsets of claims. For example, "age greater than 21" could be delivered rather than date of birth. It also supported "zero-knowledge proofs," a cryptographic method that used multiple iterations to prove authenticity.
Higgins R-Cards (Relationship Cards)
An r-card was an enhanced version of managed cards (m-cards) and personal cards (p-cards). It set up a data synchronization relationship between the user and the relying party. A change at either side updated the other. See identity metasystem
and Windows CardSpace