If you do not trust the owners of instant messengers and sometimes you need additional data encryption. For example, you need to send a photo of documents, but so that only the recipient sees it, then this application is for you. The сryptographer works on the principle of back to back encryption. That is, one person generates the "General" and "His" keys and sends them to the second person (You can use open communication channels). The second person introduces these keys to himself as the "General" and "Key of the interlocutor" and generates "His" key that will need to be sent to the first person. When a bunch of keys is collected, you can encrypt it using it, both text and files and decrypt them will only be the second owner of a set of keys.