Sweep formulas applying to encrypt text data

In this paper we consider for the first time the possibility of applying the tridiagonal run-through formulas for text data encryption. The encryption algorithm consists in computing the right part of a linear algebraic equations system with a tridiagonal matrix. In the problem, all the equations coefficients, the right-hand side and the solution take the values of the residues modulo a prime number p. The decryption algorithm consists in solving the SLAE on the class of prime modulo p deductions. The decryption algorithm uses the tridiagonal run method. Two theorems are proved for the algorithm correctness. Theorem 2 is a sufficient condition for correctness. Theorem 3 is the necessary conditions for correctness. Three encryptions of the text of 65, 67 symbols examples are given for illustrate the theorems applicability conditions. The keys spatial power is estimated.