Many researchers believe electronic wallets (secure storage devices that maintain account balances) are the solution to electronic commerce challenges. This paper argues for a more powerful model --- a secure coprocessor --- that can run a small operating system, run application programs, and also keep secure storage for cryptographic keys and balance information. We have built a system called Dyad, on top of a port of the Mach 3.0 microkernel to the IBM Citadel secure coprocessor. This paper describes the abstract architecture of Dyad and a general discussion of secure coprocessor implementations of a variety of electronic commerce applications: ffl Copy protection for software ffl Electronic cash (including a critique of proposed solutions for point-of-sale electronic wallet systems) ffl Electronic contracts ffl Secure postage 1 Introduction Many researchers believe electronic wallets (secure storage devices that maintain account balances) are the solution to electronic commerc...

Abstract. Metered mail provides substantial opportunities for fraud. (Indeed, losses due to meter fraud in the United States are said to exceed $100 million annually.) We apply cryptographic techniques to prevent several types of improper use of metering indicia. This paper describes a mail system that combines o-the-shelf barcode technology, tamper-proof devices, and cryptography in a fully-integrated secure franking system. This system provides protection against: 1. Tampering with postage meters to fraudulently obtain extra postage� 2. Forging and copying of postal indicia� 3. Unauthorized use of postage meters � and 4. Stolen postage meters. We provide detailed justi cation for our design, and discuss important tradeo s involving scanning strategies, encryption technology and 2-D barcode technology.