However, despite this wide range of standardisation activity, the ISO/IEC JTC1/SC27 work is unique in being both truly international and also aimed at general applications. As such, while we mention the relevant work of other standards bodies, the main focus of this chapter is the work of ISO/IEC JTC1/SC27. The main purpose of this chapter is to bring the international standards for cryptographic techniques to the widest possible audience. Adoption of these standards, which have received detailed scrutiny from experts worldwide, can only help to improve the quality of products incorporating security features. Note that much of the work described in this chapter is based on recent research. For brevity, references to research papers are not included here. For further information the interested reader should consult the bibliographies in the quoted standards, or the excellent encyclopaedic work (Menezes, van Oorschot and Vanstone, 1997).