From CryptoDox, The Online Encyclopedia on Cryptography and Information Security
Public key infrastructure (PKI) is an arrangement which provides for third-party vetting of, and vouching for, user identities. It also allows binding of public keys to users. This is usually carried out by software at a central location together with other coordinated software at distributed locations. The public keys are typically in Certificates.
Such infrastructure can be used to further build functionalities enabling e-government services.
PKI at Wikipedia