Method and apparatus for securely booting from an external storage device

Abstract

Techniques to securely boot up an electronics device (e.g., a cellular phone) from an external storage device are described. Secure data (e.g., a hash digest, a signature, a cryptographic key, and so on) is initially retrieved from a non-writable area of an external memory device (e.g., an one-time programmable (OTP) area of a NAND Flash device). A first program (e.g., a boot program) is retrieved from a writable or main area of the external memory device and authenticated based on the secure data. The first program is enabled for execution if authenticated. A second program may be retrieved from the main area of the external memory device and authenticated based on the secure data. The second program is enabled for execution if authenticated. Additional programs may be retrieved and authenticated. Each program may be authenticated using a secure hash function, a digital signature, and/or some other cryptographic technique.