utterly integrated with the unit of account function, so that, given the integrity of the public key system on which these are based, they become to that degree inseparable. This has clear advantages – counterfeiting is difficult or impossible unless the whole system is compromised, say by a new factoring algorithm. But at that point, the entire system is broken and the whole infrastructure is obsolete – new keys must be re-generated and the new system will also depend on some assumptions about difficulty of factoring. Due to this inherent fragility, which is even more profound with electronic voting, some economists argue that units of account should not ever be abstracted or confused with the nominal units or tokens used in exchange. A medium is simply a medium, and should not be confused for the message. See also Authentication Cheque Commodity money Forgery History of money Identity theft Private currency References Bibliography Jones, Robert A. "The Origin and Development of Media of Exchange." Journal of Political Economy 84 (Nov. 1976): 757-775. External links Linguistic and Commodity Exchanges-Examines the structural differences between barter and monetary commodity exchanges and oral and written linguistic exchanges. Currency