Asymmetric cryptography is a powerful tool (when used correctly!) that is essential to much of the security of the Internet. Within this family of techniques, the algorithms and the functionality they provide can differ greatly. But the characteristic they all have in common is key-pairs. That is, for each of these algorithms, there are two keys: a public key and a private key. For this reason, these approaches are also called “public key cryptography.”
In asymmetric operations, a party generates the key pair and (should) keep the private key confidential. Under almost every circumstance conceivable, the private key should not be disclosed. This is different from symmetric cryptography wherein two parties must share the key.
On the other hand, the party with the private key can distribute the public key to any party she chooses. Exactly what can be done with the key-pair depends on the algorithm. Common operations include:
A digital signature is.