How many keys are used in Public Key Encryption?

Public key encryption, also known as asymmetric encryption, utilizes two distinct keys to secure communications. One key is the public key, which can be freely shared and is used to encrypt data. The other key is the private key, which is kept confidential by the owner and is used to decrypt the data that has been encrypted with the corresponding public key. The security of this method relies on the fact that while the public key can be distributed openly, only the holder of the private key can decrypt messages meant for them.

This two-key system allows for secure exchanges of information between parties without needing to share a common secret. It enables functionality such as digital signatures, where a message can be signed with a private key and verified with a public key, ensuring both authenticity and integrity.

In contrast, one key alone or a combination of three distinct types of keys, such as a shared key (which is typically used in symmetric encryption), does not apply to the public key encryption system.