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Computing (FOLDOC) dictionary
Certificate Authority
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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 department. The Certificate
Authority's chief function is to verify the identity of
entities and issue digital certificates attesting to that
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 cryptographicallystrong, e.g. MD5.