Good article. I'd like more technical details, especially security related, as some pretty hard problems must have been solved to implement such system where every error or vulnerability might costs tons of money. Any recommendations?
How it actually works is theres a Message Queue (IBM MQ) that is connected over dedicated lines (MPLS or point to point, but not over the internet).
Each side uses a couple of layers of Crypto, including using Hardware Security Modules (HSMs) to actually encrypt and sign the messages.
The crypto signatures also have legal standing in a sense, if the message is valid and signed then the counter party or agency bank is authorised to process it.