Remote Digital Signing for Mobile Commerce

Mobile agents (MAs) are a promising technology which directly address physical limitations of mobile devices such as limited battery life, intermittent and low-bandwidth connections, with their capability of providing disconnected operation. This chapter addresses the problem of digital contract signing with MAs, which is an important part of any mobile commerce activity and one special challenging case of computing with secrets remotely in public. The authors use a multi-agent model together with simple secret splitting schemes for signing with shares of a secret key carried by MAs, cooperating to accomplish a trading task. In addition to known key splitting techniques of RSA, authors introduce similar techniques for El Gamal and DSS public key cryptosystems. The objective is to achieve a simple and ubiquitous solution by using the well-known public-key cryptosystem implementations, which conform to the established standards.