Signed ECB euro reference exchange rate

European Central Bank euro reference rate for any pair among the ~30 currencies the ECB publishes, returned with a SHA-256 of the exact upstream bytes, the read time, and an Ed25519 signature. Non-EUR pairs are crossed via EUR and the derivation is stated, because that cross is Soren's calculation and not an ECB figure. The ECB publishes these free of charge; the attestation is what is sold.