Self-authorizing cards and cellular network adapters for authorization of financially payments and other secure transactions. In some embodiments a smart card is provided with a connector for a USB port on a computer terminal such as a personal computer (PC). Embodiments are also provided for mobile phones, personal digital assistants (PDAs), and similar devices. The self-authorizing devices typically include a secure element that has been previously provisioned with information about a particular card holder account. A secure element reader interrogates the smart element and derives information needed to authorize the transaction. A communications controller transmits the information to a host device, such as a PC, PDA, or a mobile phone.