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There is a re-emerging demand for low-end devices such as 8-bit processors, driven by needs for pervasive applications like sensor networks and RF-ID tags. Security in pervasive applications, however, has been a major concern for their widespread acceptance. Public-key cryptosystems (PKC) like RSA and DSA generally involve computation-intensive arithmetic operations with operand sizes of 1024− 2048 bits, making them impractical on such constrained devices. Elliptic Curve Cryptography (ECC) which has emerged as a viable alternative is a favored public-key cryptosystem for embedded systems due to its small key size, smaller operand length, and comparably low arithmetic requirements. However, implementing full-size, standardized ECC on 8-bit processors is still a major challenge and normally considered to be impracticable for small devices which are constrained in memory and computational power.

The thesis at hand is a step towards showing the practicability of PKC and in particular ECC on constrained devices. We leverage the flexibility that ECC provides with the different choices for parameters and algorithms at different hierarchies of the implementation. First a secure key exchange using PKC on a low-end wireless device with the computational power of a widely used 8-bit 8051 processor is presented. An Elliptic Curve Diffie-Hellman (ECDH) protocol is implemented over 131-bit Optimal Extension Field (OEF) purely in software. A secure end-to-end connection in an acceptable time of 3 seconds is shown to be possible on such constrained devices without requiring a cryptographic coprocessor.