04926480 is referenced by 320 patents and cites 16 patents.

A user controlled card computer C and communicating tamper-resistant part T are disclosed that conduct secure transactions with an external system S. All communication between T and S is moderated by C, who is able to prevent T and S from leaking any message or pre-arranged signals to each other. Additionally, S can verify that T is in immediate physical proximity. Even though S receives public key digital signatures through C that are checkable using public keys whose corresponding private keys are known only to a unique T, S is unable to learn which transactions involve which T. It is also possible for S to allow strictly limited messages to be communicated securely between S and T.

Title
Card-computer moderated systems
Application Number
123703
Publication Number
4926480
Application Date
May 24, 1988
Publication Date
May 15, 1990
Inventor
David Chaum
14652 Sutton St., Sherman Oaks, 91403
CA, US
Agent
Nixon & Vanderhye
IPC
H04K 1/00
View Original Source