Basic Encryption

There are two types of encryptions: symmetric and asymmetric.

In a symmetric encryption, one secret key is generated, and that very same key is shared between the sender and receiver. Databases benefit from using symmetric encryptions, as they are much faster to use as opposed to the asymmetric alternative. AES is one of the most popular symmetric encryption algorithms.

In asymmetric encryptions, two keys are generated; private and public. The public key is used to encrypt the data, and the private key is used to decrypt the data. Hence, asymmetric encryptions are excellent when encryption is desired between two different endpoints. For example, when the web browser wants to send encrypted data to a web server, the web server will have the private key at hand to decrypt the incoming data, while the web browser (client) will encrypt data with the public key. ECC, RSA and DSA are some popular asymmetric encryptions, which are used in popular tools such as Git.

おまけ: http://www.moserware.com/2009/09/stick-figure-guide-to-advanced.html