we prove that the class of profinite groups $g$ that have a factorization $g=ab$ with $a$ and $b$ abelian closed subgroups, is closed under taking strict projective limits. this is a generalization of a recent result by k.h.~hofmann and f.g.~russo. as an application we reprove their generalization of iwasawa's structure theorem for quasihamiltonian pro-$p$ groups.

We consider several novel aspects of unique factorization in formal languages. We reprove the familiar fact that the set uf(L) of words having unique factorization into elements of L is regular if L is regular, and from this deduce an quadratic upper and lower bound on the length of the shortest word not in uf(L). We observe that uf(L) need not be context-free if L is context-free. Next, we con...

We present new, e cient algorithms for some fundamental computations with nite dimensional (but not necessarily commutative) associative algebras over nite elds. For a semisimple algebra A we show how to compute a complete Wedderburn decomposition of A as a direct sum of simple algebras, an isomorphism between each simple component and a full matrix algebra, and a basis for the centre of A. If ...

We propose a generalization of an RSA-like scheme based on Rédei rational functions over the Pell hyperbola. Instead of a modulus which is a product of two primes, we define the scheme on a multi-factor modulus, i.e. on a product of more than two primes. This results in a scheme with a decryption which is quadratically faster, in the number of primes factoring the modulus, than the original RSA...

Pk -factorization of a complete bipartite graph for k, an even integer was studied by H. Wang [1]. Further, Beiling Du [2] extended the work of H.Wang, and studied the P2k-factorization of complete bipartite multigraph. For odd value of k the work on factorization was done by a number of researchers[3,4,5]. P3-factorization of complete bipartite graph was studied by K.Ushio [3]. P5-factorizatio...

A palindrome is a symmetric string, phrase, number, or other sequence of units sequence that reads the same forward and backward. We present an algorithm for maximal palindromic factorization of a finite string by adapting an Gusfield algorithm [15] for detecting all occurrences of maximal palindromes in a string in linear time to the length of the given string then using the breadth first sear...

A major obstacle to implementing Shor’s quantum number-factoring algorithm is the large size of modular-exponentiation circuits. We reduce this bottleneck by customizing reversible circuits for modular multiplication to individual runs of Shor’s algorithm. Our circuit-synthesis procedure exploits spectral properties of multiplication operators and constructs optimized circuits from the traces o...

We describe a modification to the well-known large prime variant of the multiple polynomial quadratic sieve factoring algorithm. In practice this leads to a speed-up factor of 2 to 2.5. We discuss several implementation-related aspects, and we include some examples. Our new variation is also of practical importance for the number field sieve factoring algorithm. 1. Factoring with two large prim...

On February 2, 1999, we completed the factorization of the 140–digit number RSA–140 with the help of the Number Field Sieve factoring method (NFS). This is a new general factoring record. The previous record was established on April 10, 1996 by the factorization of the 130–digit number RSA–130, also with the help of NFS. The amount of computing time spent on RSA–140 was roughly twice that neede...

We describe an adaptation of the number field sieve to the problem of computing logarithms in a finite field. We conjecture that the running time of the algorithm, when restricted to finite fields of an arbitrary but fixed degree, is Lq[1/3; (64/9)1/3 + o(1)], where q is the cardinality of the field, Lq [s; c] = exp(c(log q)s(log log q)1−s), and the o(1) is for q →∞. The number field sieve fact...