Public Key Infrastructure

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Public Key Infrastructure

(cryptography, communications)
(PKI) A system of public key encryption using digital certificates from Certificate Authorities and other registration authorities that verify and authenticate the validity of each party involved in an electronic transaction.

PKIs are currently evolving and there is no single PKI nor even a single agreed-upon standard for setting up a PKI. However, nearly everyone agrees that reliable PKIs are necessary before electronic commerce can become widespread.



IETF PKIX Working Group.
This article is provided by FOLDOC - Free Online Dictionary of Computing (


(Public Key Infrastructure) A framework for creating a secure method for exchanging information based on public key cryptography. The foundation of a PKI is the certificate authority (CA), which issues digital certificates that authenticate the identity of organizations and individuals over a public system such as the Internet. The certificates are also used to sign messages (see code signing), which ensures that messages have not been tampered with. For more on how certificates and public keys are used, see digital certificate.

In-house PKIs
A PKI can also be implemented by an enterprise for internal use to authenticate employees accessing the network. In this case, the enterprise is its own certificate authority (CA). For details on the public key system, see cryptography.

Managing the Root Key
The root key is the public/private key pair of the certificate authority. If the private part of that root key is ever discovered, all the certificates issued under that key pair are compromised. Creating and keeping the private key very private is critical.

All Encompassing
The PKI establishes the encryption algorithms, levels of security and distribution policy to users. The PKI embraces all the software (browsers, email programs, etc.) used to support the process by examining and validating the certificates and signed messages. See digital certificate, digital signature, root key, web of trust and DST.

Keeping the Root Key Secure
Gemalto's Luna is a line of hardware security module (HSM) products that generate the root key in a PKI system and keep the private key secure. (Image courtesy of Gemalto NV,
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