FIELD: cryptography, electronic mass service systems. SUBSTANCE: method involves masking source data to be used in electronic mass service systems with unlimited number of signature types under condition that they do not require increase in number of technical resources, mass data storage equipment and search in them. Said method and device provide high level of security and unexpected value of digital RSA signature, because data features, which ensure security can be checked directly by applicant. The method involves sequence of operations for masking source data by means of their RSA encryption and decryption of authorized masked data. EFFECT: increased security, decreased probability of expected signature, increased speed of encryption. 54 cl, 17 dwg, 12 ex
