Public-key infrastructure (PKI) was developed mainly to support secure information exchanges over unsecure networks. It has been used to ensure that the person identified as sending a transaction is the originator, that the person receiving the transaction is the intended recipient and that the transaction data has not been compromised. PKI requires a system for generating and managing digital certificates that identify the holders (people, systems or devices) of assigned public and private key pairs, which is useful for identification, authentication, encryption and digital signing. Enterprise PKI refers to the use of this system over enterprise intranets, and involves the issuance of digital certificates to individual users, servers and services, and software tools that assist with enrollment, integration with directory services, managing keys, and renewal and revocation of certificates.