Hello, Submitter, you wrote: S> As I am very far from this subject, eyes run up looking at various libraries and methods of enciphering of the text. S> it is necessary to save the text data a disk, but it would not be desirable in the pure state (that any interested person could look at them pushing F3), it would be desirable not so difficult (but it is possible also difficult) the encryption algorithm and an application example to it. S> Can give the reference to such source code where at first on an input the text which is encoded is given, and then it is decoded reversely. S> quite would approach RSA, truth I do not know that it. Greetings It is necessary the nobility at qualitative level and to distinguish all main concepts of cryptography. Well, i.e. without understanding of the main modern concepts be not put at all not only in bowels of algorithms, but also to interfaces of libraries. Otherwise your work, very possibly, will not cost the eaten away egg since the competent expert finds an error in the receptions used by you and at one stroke crosses imaginary protection. It concerns illiterate usage reliable and widespread tools. Further, about low-level libraries (by experience) openssl, libressl - at once is not present. Yet you do not know, for what it is required to you, it is not necessary. , it is not necessary to use as a default. botan - library of algorithms. All is, if know that it is necessary for you - take and use. libsodium - here that is necessary for you. Certainly, always it is necessary to read the documentation. Also consider, the documentation on cryptography has property to become outdated, i.e. articles and recommendations 00 should be considered years very much critically, especially concerns quantitative informations and a level of reliability of those or other algorithms. But, we address to an initial message. What task? Perhaps it is necessary to use more high-level decisions? For example, gnupg - a tooling of command line for enciphering, signatures and everything that is connected to enciphering of files and messages. Quite probably to cause it from your program. Than not a variant?