anonymous settlement

Also, for anonymous payment for such overseas services, anonymous transfer in at least one of the two currencies is necessary.

The last point is certainly not true. If user X communicates with service A (a gateway) in one country to purchase something from service B in another country, X can settle accounts with A anonymously (say in US$) and then A and B can settle accounts with one another (say in sterling) openly. May I point out that that in your example that X and A are performing an anonymous transfer in dollars, which is one of the two currencies? Eric