One of the most common methods currently protect information is encryption. Ready to transfer data message , initially open and unprotected , encrypted and thus converted into a coded telegram , ie in a closed text or image document. As such, the message is transmitted over a communication channel , not even protected. Authorized user after receiving a message decrypts it by the inverse transform of the cryptogram , thereby obtaining the source , open view messages available to authorized users perception.
This method uses a special algorithm which starts operation unique number ( sequence of bits ), typically referred to as ciphering key. To exchange encrypted data has been successful, both the sender and receiver must know the correct key setup and keep it a secret.
Resistance of any system of close-coupling determined by the degree of secrecy used her key. However, this key must be known to other users on the network so that they can freely exchange encrypted messages. In this sense, the cryptographic system also help solve the problem of authentication ( authentication ) of the received information. Burglar in case of interception, the message will only deal with the ciphertext , and the true recipient , taking messages , known to him and closed the sender key will be securely protected from possible misinformation.
There are two types of cryptographic algorithms : classical algorithms based on the use of closed , secret keys , and new public-key algorithms , which use one public and one private key (these are also called asymmetric algorithms ).