<cryptography, body> (CA or "Trusted Third Party") An entity (typically a company) that issues digital certificates to other entities (organisations or individuals) to allow them to prove their identity to others.
A Certificate Authority might be an external company such as VeriSign that offers digital certificate services or they might be an internal organisation such as a corporate MIS
The Certificate Authority's chief function is to verify the identity of entities and issue digital certificates attesting to that identity.
The process uses public key cryptography to create a "network of trust".
If I want to prove my identity to you, I ask a CA (who you trust to have verified my identity) to encrypt a hash
of my signed key with their private key. Then you can use the CA's public key to decrypt the hash and compare it with a hash you calculate yourself.
Hashes are used to decrease the amount of data that needs to be transmitted.
The hash function must be cryptographically strong, e.g. MD5