Another is a full-frontal assault in which crackers try to break the code by guessing millions of possible keys until the right one is found. A fast computer is capable of trying millions of guesses in seconds, but the process is still no walk in the park. In symmetrical encryption, the same secret key is used to both encrypt and decrypt a message. Symmetric algorithms present problems for users who have never met or exchanged keys. Public Key Cryptography Public key cryptography is also known as asymmetric cryptography.
Keys come in pairs.
One key is public, widely available. The other, private key is a closely guarded secret. To send a secure message, one looks up the recipient's public key and uses it to encrypt the message. The message then can be sent over an unsecured channel without fear of interception. The private key is necessary to decode it.