Introduction.- Mathematical Background.- Groups, Rings, Fields.- Elliptic Curves.- Scalar Multiplication.- Fast Computation Methods of Scalar Multiplication.- Efficient Arithmetic on Subfield Elliptic Curves Over Small Finite Fields of Odd Characteristic.- Explicit Lower Bound for the Length of Minimal Weight Expansions on Koblitz Curves.- Lower Bound for the Length of Minimal Weight Expansions on Koblitz Curves.- Another Proof of the Minimality of the Hamming Weight.- Minimal Length Form on Koblitz Curves and its Cryptographic Application.