This dilemma is solved by the asymmetrical method. Here, all who want to exchange encrypted data create two keys that belong together: one public and one private. The public key is forwarded, the private is kept under lock and key. Anyone who now wants to send an encoded message to recipient A takes the public key from A, encodes the message using that key, and sends it to A.

Decrypting is not possible without the private key of A; the public key can be used only for encoding. In addition, the private key can also be used for signing messages. So in case B wants to send an encoded and signed message to A, he will encode it using the public key of A and sign it with his private key. If A has
B's public key, he can check the authenticity of the digital signature.