US Patent 7765399 Computer architecture for a handheld electronic device

Mobile PDA computer system (300) includes a non-secure processor (306), comprising an untrusted microprocessor and an untrusted operating system executing on the untrusted microprocessor. The system also includes a secure processor (302), comprising a trusted microprocessor and a trusted operating system executing on the trusted microprocessor. A cryptographic engine (304) is provided for encrypting and decrypting data. A first data communication link (303) communicates data between the secure processor and the cryptographic engine. A second data communication link (305) communicates data between the non-secure processor and the cryptographic engine. In this way, the cryptographic engine forms a bridge between the secure user processor and the non-secure user processor.