You can encrypt a particular line (in which case everything sent on that line is encrypted) or a particular transmission. End-to-end encryption is the process of encrypting a teleprocessing line. You encrypt a teleprocessing line by using cryptographic modems. When using ACF/VTAM, there are software products you can use to encrypt individual sessions. You can also use software products to encrypt specific transmissions before sending them through the network. In this case, the receiver must have the same product and the encryption key to decode the data. When using TCP/IP for doing NJE, you can define a policy agent for the network and exchange digital certificates between nodes in network.