In the open networks (e.g. Internet) the messages go through systems controlled by different service providers, thus not only the addressee might get access to them. The aim of increasing security is that the sender and the receiver could unequivocally be identified; the original message could not be changed as well as others could not access it. The most up-to-date technical solution for this problem is asymmetric (also named public key) encryption procedure and its most widespread version RSA. (The letters RSA are the initials of the surnames of the describers = Ronald Rivest, Adi Shamir, Leonard Adlemann.)

Advantage of the public key encryption is that the coding party (sender) and the decoding party (receiver) do not have to exchange a secret password or key. Instead every user has a key pair ensuring secure communication. One of the keys is private while the other is public. The two keys are derived from the same key generation procedure; they belong completely to each other, but none of them can be concluded from the other. Every user must keep his/her private key confidential, while the public key has to be presented to everyone with whom you wish to communicate (e.g. by means of the so-called key data base available for everyone). In case of asymmetric encryption the communicating parties need no reliable channel or personal meeting, only the authenticity of the key and the connection with the owner have to be proved.

During the encryption process the data are encrypted (encoded) by the public key belonging to the encrypting certificate of the receiving party while on the receiving side decoding is possible only by the private counterpart of the public key used for encrypting.

For the above reason the encrypted data can only and exclusively be interpreted/read by the person who has the private counterpart of the public key. Accordingly private encrypted data can only be sent to the person who has a valid encryption certificate issued by a reliable Certification Authority.

The process of encryption can be seen below:

The process of decoding can be seen here: