Currency management system and electronic signature device

A secret key type electronic signature device, comprising:

• at least one memory storing a cryptographic key in association with a first authority and a second authority which are assigned to the cryptographic key, wherein the first authority is different from the second authority and the second authority is only for verification of an electronic signature;
• and
• at least one processor configured to:
• share the cryptographic key with another electronic signature device;
• wherein the other electronic signature device comprises at least one processor and at least one storage, and the at least one processor of the other electronic signature device is configured to store, in the at least one storage of the other electronic signature device, the shared cryptographic key and the second authority assigned to the shared cryptographic key,
• wherein the at least one processor of the other electronic signature device is configured to perform verification of the electronic signature using the shared cryptographic key, but cannot perform creation of the electronic signature using the shared cryptographic key, and
• wherein the first authority and the second authority both stored in the memory of the secret key type electronic signature device are configured for creation and verification of the electronic signature;
• wherein the at least one processor of the secret key type electronic signature device is further configured to:
• perform creation of a first electronic signature using the shared cryptographic key stored in the secret key type electronic signature device according to the first authority assigned to the shared cryptographic key stored in the secret key type electronic signature device that authorizes the creation, and as a result, attach the created first electronic signature to a piece of information;
• wherein the at least one processor of the other electronic signature device is further configured to:
• perform verification of the first electronic signature attached to the piece of information using the shared cryptographic key stored in the other electronic signature device according to the second authority assigned to the shared cryptographic key stored in the other electronic signature device that authorizes the verification, and, as a result, determine whether the piece of information to which the first electronic signature is attached has been illegally changed based on the result of the verification;
• and
• not perform creation of the first electronic signature using the shared cryptographic key stored in the other electronic signature device according to the second authority assigned to the shared cryptographic key stored in the other electronic signature device that does not authorize the creation, and, as a result, not attach the first electronic signature to the piece of information.