13.4 Network Layer Cryptography

Network layer cryptography leaves enough of a packet in plaintext to allow routing through the internet, while still protecting the actual data as it travels between hosts. In the internet community, the standard network layer protocol is IPsec, the IP Security Protocol.

Evolution of Network Layer Encryption

IPsec is not the only network layer encryption protocol, nor is it the first. The DOD commissioned a network-layer encryption system for the ARPANET, called the “private line interface.” With the deployment of internet protocols, the NSA promoted a series of protocol standards, called the Secure Data Network System (SDNS), that included a protocol similar to IPsec called “Security Protocol 3” (SP3

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