Chapter Summary

In this chapter, we describe some standards for representation of cryptographic data in various formats and for conversion of data among different formats. We also present some standard encoding and decoding schemes that are applied before encryption and after decryption. These standards promote easy and unambiguous interfaces with the cryptographic primitives described in the previous chapter.

The IEEE P1363 range of standards defines several data types: bit strings, octet strings, integers, prime finite fields, finite fields of characteristic 2, extension fields of odd characteristics, elliptic curves, elliptic curve points and polynomial rings. The IEEE drafts also prescribe standard ways of converting data among these formats. For example, the primitive BS2OS converts a bit string to an octet string, the primitive FE2I converts a finite-field element to an integer.

We subsequently mention some of the public-key cryptography standards (PKCS) propounded by RSA Laboratories. Draft PKCS #1 deals with RSA encryption and signature. In addition to the standard RSA moduli of the form pq, it also suggests possibility of using multi-prime RSA, that is, moduli which are products of more than two (distinct) primes. The draft recommends use of the optimal asymmetric encryption procedure (OAEP). This probabilistic encryption scheme provides provable security against chosen-ciphertext attacks. A probabilistic signature scheme is also advocated for use. These probabilistic schemes call for using a mask-generation function (MGF). A concrete realization of an MGF is also provided. Draft PKCS #3 standardizes the Diffie–Hellman key exchange algorithm.