Pseudo-probabilistic encryption is presented as a new algorithmic mechanism for ensuring information security, which implements information protection in the event of attacks with compelling disclosure of the encryption key. The basic requirement for transformations of this type is the computational indistinguishability of the ciphertext from probabilistic encryption. We consider methods and algorithms that implement pseudo-probability encryption as a simultaneous cryptographic transformation of fi ctitious and secret messages in two different keys, consisting in the formation of blocks of intermediate ciphertexts and their reversible mapping into a single extended block of the output cryptogram. Algorithms are proposed that include the task of the unifying mapping procedure in the form of solutions of systems of linear equations and comparisons in which numbers and binary polynomials are used as a module. The proposed methods have a suffi ciently high productivity and are of considerable interest for practical application in information security systems.