Abstract: Methods and apparatuses are disclosed for conducting secure transactions via postal authority cryptographic transformations. In particular, value is issued in the form of a value message including a cryptographic transformation enabling a recipient to determine the authenticity of the value message. The recipient applies additional cryptographically transformed information to endorse the value message. The postal authority, receives the endorsed value message, cryptographically transforms the value message, and registers the transfer of value from the payor to the payee. Similarly, the cryptographic transformations can be used to protect the identity of a mail order customer while ensuring the authenticity of a purchase order and payment by a customer to a mail order merchant. In yet another application, the cryptographic transformations facilitate payment of bills via submission of “endorsed” postcards to the postal authority.