The increasing acceptance of electronic mail as a business tool has revealed a few problems which have not been manifested in its nonelectronic counterpart. Thus, the signing of a contract between two parties necessitates the electronic exchange of signatures between those parties. The authors of this paper have developed a procedure by which this may be reliably accomplished. An Oblivious Transfer protocol is outlined for this purpose, and this in turn employs a Partial Secrets Exchange subprotocol, employing any appropriate Public Key Encryption system.

A similar procedure may be applied to the receipt of certified mail; acknowledgment is generated if and only if the receiver has received an entire message. A further protocol is outlined for the electronic flipping of a coin (where the parties are not co-located and must communicate through some sort of network). The approach is thorough, and a comprehensive set of references is included. The paper will be invaluable for anyone concerned with cryptosystems and their applications.