Methods, systems, and computer-readable storage mediums are described for effecting practical use of a dual currency which is a currency that can be electronically created and stored, and further for which there is a secret key (e.g., the secret key of a public key/secret key pair as used in public key cryptography) such that: an entity that does not possess the secret key cannot, in practice, create notes of the currency; and an entity that does possess the secret key can, in practice, create notes of the currency without assistance from entities that do not possess the secret key.