For the most security they are calculated from random number generators. LockBox provides support for the most well known asymmetric algorithm, RSA , as well as support for most well known symmetric algorithms, including DES, triple-DES, Blowfish, and Rijndael, the new Advanced Encryption Standard. Asymmetric algorithms, on the other hand, use one key for encryption and another for decryption. The two keys are related in a mathematical sense. Yet, even if one of the keys is known, it is very hard to calculate the other.
Asymmetric algorithms are popular because the keys can be published.
This published key is known as the public key . Public keys allow anyone to use the key to encrypt a message and send it to a recipient. The only person who can decrypt the message is the recipient because the recipient is the only one who knows the other key, which is known as the private key . Hence, anybody can send an encrypted message, even people unknown to the recipient. The transmission of this secret key could be intercepted, removing any security.