We present an exposition of the basic properties of the Jacobi symbol, with a method of calculating it due to Eisenstein. Fix a prime p. For an integer a relatively prime to p the Legendre symbol is defined by (a/p) = 1 if a is a quadratic residue (mod p) and (a/p) =−1 if a is a quadratic nonresidue (mod p). We recall Euler’s theorem that (a/p) ≡ a(p−1)/2 (mod p). We have the famous Law of Quad...

Duadic codes were introduced by Leon et al. [5] as cyclic codes generalizing quadratic residue codes. Brualdi and Pless generalized them to polyadic cyclic codes [2] and Rushanan did so to duadic Abelian group codes [9]. Theorems concerning the existence of these codes in terms of field and group restrictions have been proved during this development, beginning with the one of Smid for cyclic du...

= 1 or −1 according as j is or is not a quadratic residue mod p. A multivariable generalization of Theorem 1.1 follows. Theorem 1.1 is a special case of Theorem 1.2 with x3 = · · · = xp = 0. Theorem 1.2. Let p be an odd prime and p = (−1)(p−1)/2p. Then there exist integer polynomials R(x1, x2, . . . , xp) and S(x1, x2, . . . , xp) such that 4 · det(circ(x1, x2, . . . , xp)) x1 + x2 + · · ·+ xp ...

A general type of linear cyclic codes is introduced as a straightforward generalization of quadratic residue codes, e-residue codes, generalized quadratic residue codes and polyadic codes. A generalized version of the well-known squareroot bound for odd-weight words is derived.

Recently, a new algebraic decoding method was proposed by Truong et al. In this paper, three decoders for the quadratic residue codes with parameters (71, 36, 11), (79, 40, 15), and (97, 49, 15), which have not been decoded before, are developed by using the decoding scheme given by Truong et al. To confirm our results, an exhaustive computer simulation was executed successfully.

A prime number p is called elite if only finitely many Fermat numbers 2 n + 1 are quadratic residues of p. Previously only the interval up to 10 was systematically searched for elite primes and 16 such primes were found. We extended this research up to 2.5 · 10 and found five further elites, among which 1 151 139 841 is the smallest and 171 727 482 881 the largest.

In the book which accompanies the stencils various methods of finding quadratic residues are discussed and the method by means of the expansion of the square root of the number in a continued fraction is found to be by far the most effective. Various examples are given illustrating the power of the stencils, and a reproduction of the first page of the list of primes accompanies the work. The pl...

In [1] a proof was given of Fermat’s Two-Square Theorem using the group theoretical structure of the classical modular group. This has been extended in many directions and to other square properties in general rings. In particular in [2] a two-square theorem was given for the Gaussian integers in terms of when ii is a quadratic residue. In this note we examine and survey this technique and the ...

Let π(x; d, a) denote the number of primes p ≤ x with p ≡ a(mod d). Chebyshev’s bias is the phenomenon that ‘more often’ π(x; d, n) > π(x; d, r), than the other way around, where n is a quadratic non-residue mod d and r is a quadratic residue mod d. If π(x; d, n) ≥ π(x; d, r) for every x up to some large number, then one expects that N(x; d, n) ≥ N(x; d, r) for every x. Here N(x; d, a) denotes ...

We discuss two combinatorial problems for which we have only sub-optimal solutions. We describe known solutions and we explain why better solutions would be of importance to Cryptography. The areas of application are in improving the ef-ciency of Zero-Knowledge proofs, in relating the quadratic residuosity problem to the problem of integer factorization, and in analyzing some cryptographic sche...