Symmetric encryption requires two keys: a public key and a private key. The two keys work in pair. The data encrypted with the public key can only be decrypted with the corresponding private key. As encryption and decryption require two different keys, this algorithm is called asymmetric encryption. The procedure that asymmetric encryption executes the exchange of classified information is: party A generates a pair of keys and releases the public key, and the party B intending to send information to party A will encrypt the information with it, and then send back to party A; the party A will decrypt the information sent by party B with its own private key. When the party A wants to answer party B, the procedure goes the other way around, which means, it uses party B’s public key to encrypt the information, and vice versa, the party B will decrypt the information with its private key after receiving it.
On the other hand, the party A can sign the classified information with his private key before sending to the party B; and the latter can verify the signing of the information with the former’s public key.
Currently, the frequently used algorithm is Elliptic Curve Digital Signature Algorithm (ECDSA) , which is also introduced and applied by CUN.