(Public Key Infrastructure) Electronic framework for trusted security. Participants in a PKI each obtain a digital certificate from a trusted Certificate Authority (CA), which then authenticates their identity when initiating a secure transaction. Individual transactions are encrypted by each participant using their own pair of electronic keys, one of which they keep for their own private use, while the other -- the 'public key' -- is made available to other participants. PKI has been widely adopted as the basis for secure Internet and web services transactions.