Signet

Abstract

The absence of reliable network connectivity in the developing world has resulted in the use of paper receipts remaining the de facto standard for tracking transactions of various types. This includes both cash transactions (microfinancerelated disbursements and repayments, purchases, money transfers) and noncash goods (food commodities to/from godowns or warehouses). Such receipts are susceptible to loss, damage and alteration, with the last in particular severely compromising systems which depend on quotas or disbursement and repayment. Similarly, they allow go-betweens and agents to falsify payment or disbursement information and embezzle or misdirect funds or goods. This paper describes Signet, a system which uses the computational power of commodity mobile telephones and security enabled Subscriber Identity Module (SIM) cards to create a secure and auditable record for atomic in-person transactions in the developing world. Signet performs this function at very low operating cost and without requiring continuous connectivity to a trusted third party.