FATF's Recommendation 16 (the 'Travel Rule') requires that for any transfer of value over a threshold (≈USD $1,000 in most jurisdictions), the originator institution must transmit identity data about both the SENDER and the RECEIVER alongside the actual transfer. The rule applies to wire transfers (it's been there since the 1990s) and now applies to CRYPTO transfers too, exchanges, custodians, and on-ramp fintechs must carry IVMS 101 messages with every transfer. The ledger doesn't change much, the same crypto in/out journal entries exist, but each entry needs to carry the IVMS payload as metadata, and your sending engine has to either deliver the IVMS to the counterparty or HOLD the transfer pending counterparty support.