Harvest Now, Decrypt Later

Harvest now, decrypt later describes an adversary who cannot read your traffic today and records it anyway. Storage is cheap, ciphertext keeps indefinitely, and the decryption happens whenever the mathematics gives way - which makes the relevant question not whether a quantum computer exists now, but whether the data will still be sensitive when one does. Anything with a multi-year shelf life is already in scope.

For a real-time data provider the exposure is unusual, because the records are often the least sensitive part of the capture. What never becomes public is which entities a firm subscribed to and when its interest began - a subscription list is a portfolio map, and the timing is frequently more informative than any single record inside it. That is the argument for post-quantum cryptography on every hop today rather than at a later migration, and it is why the guarantee only holds if no leg of the path belongs to somebody else.