Band 1, Heft 2

The Special Number Field Sieve factoring algorithm has a large number of parametric choices, each of which can affect its run time. We give guidelines for these choices along with a discussion of useful coding optimizations. We also give a theoretical argument which proves that the choice of sieving region that has been used so far in successful factorizations is not optimal and show how to obtain an improved sieve region. The improvement has yielded a 15% speed increase in practice.

A perfect hash family PHF( N; k, v, t ) is an N × k array on v symbols with v ≥ t , in which in every N × t subarray, at least one row is comprised of distinct symbols. Perfect hash families have a wide range of applications in cryptography, particularly to secure frameproof codes, in database management, and indirectly in software interaction testing. New recursive constructions, new direct constructions, and PHFs found using tabu search are provided here. The first general tables of the best known sizes of PHFs are presented; in the process, the known direct and recursive constructions are surveyed.

In this paper we give an overview of some of the cryptographic applications which were derived from the proposal of R. J. McEliece to use error correcting codes for cryptographic purposes. Code based cryptography is an interesting alternative to number theoretic cryptography. Many basic cryptographic functions like encryption, signing, hashing, etc. can be realized using code theoretic concepts. In this paper we briefly show how to correct errors in transmitted data by employing Goppa codes and describe possible applications to public key cryptography. The main focus of this paper is to provide detailed insight into the state of art of cryptanalysis of the McEliece cryptosystem and the effect on different cryptographic applications. We conclude, that for code based cryptography a public key of 88KB offers sufficient security for encryption, while we need a public key of at least 597KB for secure signing.