With the recent Electronic Signatures in Global and National Commerce Act, public key cryptography, digital signatures, and digital certificates are finally emerging as a ubiquitous part of the Information Technology landscape. Although these technologies have been around for over twenty years, this legislative move will surely boost e-commerce activity. Secure electronic business transactions, such as contracts, legal documents, insurance, and bank loans are now legally recognized. In order to adjust to the realities of the marketplace, other services may be needed, such as a non-repudiation...