[2] Several American States have implemented legislation which gives effect to and governs digital signatures. See the Utah Digital Signature Act of 1996. The mathematics of public key cryptography is described in Rivest, Shamir and Adleman "A method for obtaining digital signatures and public-key cryptosystems" (1978) 21 Communications of the ACM 2. The RSA algorithm is named after the authors of this paper.

[3] Blind signatures were pioneered by David Chaum who is a principal in DigiCash, the largest of the existing net payment organisations. See Chaum, D., "Privacy Protected Payments: Unconditional Payer and/or Payee Anonymity," in Smart Card 2000, North-Holland, 1989, pp. 69-92 and D.Chaum. Blind Signatures for Untraceable Payments. In Advances in Cryptology - Crypto '82 Proceedings, Plenum Press, 1983, pages 199-203

[4]See Van Der Hoek, "Digicash" in the proceedings of the First Australian Computer Money Day, conference held at the Department of Computer Science, University of Newcastle, 28 March, 1996.

[5] ⁵ The method described here is that of Pierce. See M. Peirce, PayMe: Secure Payment for World Wide Web Services, B.A. (Mod) Project Report, Computer Science Department, Trinity College Dublin, Dublin 2, Ireland. May 1995

[6] For the concept of "Digital signature" see the previous article in this series, Virtual Cash in XXXXXXXX.

[7] See "Smart Cards", (1995) 6 JBFLP 297 - 299

[8] See "Smart Cards" (1995) 6 JBFLP 297 for a discussion of the confused terminology relating to "open" and "closed" smart card systems.

[9] This is not, of course, entirely true. When the entire system collapses it may be necessary to resort to general law principles to unravel liabilities. So, for example, if the card issuer fails, it may be necessary to consider the legal nature of payment by credit card; see Re Charge Card Services Ltd [1986] 3 All ER 289 and generally, Tyree, Banking Law in Australia, Butterworths, 1995 at p. 300.

[10] These general promises are not without precedent since they are quite similar to the promise made by a bank who issues a "negotiable" documentary letter of credit: see Banco Nacional Ultramiarino v First National Bank of Boston 289 F 169 (1923) for a classical example. By analogy with the letter of credit, there may be some "fraud exception" which could apply to the presentment of digital coins.

[11]Bank notes were the common form of currency in Australia until the first issue of the Commonwealth notes in 1910. This was accompanied by the imposition of a tax on bank notes which led to their rapid demise although bank notes were issued in Tasmania until the 1930s. See Tyree, Banking Law in Australia, Butterworths, 1995, p2.