Abstract: A method and apparatus is provided for secure terminals that facilitate secure data transmission and are compliant with the payment card industry (PCI) data security requirements. A security processor is combined with an application processor and a display into a secure display control unit (SDCU) that provides tamper resistance and other security measures. Modular secure I/O devices are interfaced to the SDCU via a wired, or wireless, medium so as to facilitate secure data transfer to the SDCU during a point-of-sale (POS) transaction or other transaction that requires secure data entry. The secure I/O devices implement one-time-pad (OTP) encryption, where the random keys, or pads, are generated by a derived unique key per transaction (DUKPT) generator. Other embodiments facilitate interconnection of the secure I/O devices to a hardware security module (HSM) or a personal computer (PC) while maintaining a high level of data security.