Asymmetrical encryption methods have quickly become established due to the security they offer. However, security has its price: Asymmetrical encryption methods are slow. The mathematics involved in the encryption and decryption of messages is far more complex that with symmetrical encryption methods and thus require more computing time—a critical factor when transmitting larger quantities of data.
The advantages of symmetrical and asymmetrical encryption can be used in suitable combinations of these methods. In this way, the higher security of the asymmetrical encryption is used to protect the transmission of the secret key. The actual data for transmission are then encrypted with the faster symmetrical method.
- First of all, Bob generates a key pair and publicizes the public key.
- Alice uses the public key to encrypt a secret symmetrical key and sends this to Bob. For each transmission, this secret key is newly defined according to a random procedure.
- Bob is the only one who can decrypt this secret key by using his private key.
- Alice and Bob then use this secret key to encrypt and decrypt the clearly much larger volume of the payload data.