It can also be used to allow the transfer of information between two parties using a communication medium which is known to be insecure, such as email and the Internet. In a scenario where Alice wants to send a message to Bob, she will obtain Bob s public key from the public domain, encrypt the message with it, and sends it across to Bob via email. Cryptography is the science of disguising information by transforming a piece of data into something which seems totally meaningless. Encryption, for example, is a form of cryptography. It uses electronic keys, which may be symmetric or asymmetric.
Symmetric cryptography uses a common key that is randomly generated for each session.
The encryption process is fast, and if the key length is long enough, is also safe. However, as a different key is generated each time a session takes place, administration of such keys will be very cumbersome for frequent sessions with multiple parties. Potentially, security of the sessions will also be compromised as more parties are exposed to the same key for encryption and signing. The public key is kept in a public domain, and available for public access, while the private key is kept by the subscriber and known only to him. An action done by one of the keys can only be undone by the corresponding key within the key pair.