Such as...? To me, passing around a long unstructured numeric string is a lot more error-prone than selecting a contact from my banking app, or writing a short

Such as...? To me, passing around a long unstructured numeric string is a lot more error-prone than selecting a contact from my banking app, or writing a short, structured phone number or email address. In any case, the recipient needs to know the secret one-word answer to the question set by the sender, which would prevent wrong parties from claiming money (this can be skipped if the recipient registered their phone number or email address forbauto-deposit).