Network Security Principles and Practices

Encryption and Integrity-Checking Mechanisms in IPsec

As soon as the IPsec SAs are established, the next step is to start performing the encryption using DES or 3DES encryption if ESP was set up as the encapsulation mechanism. In addition to encryption, both ESP and AH require that integrity checking hashes be included in the packets. This section discusses how encryption and integrity checking work.

Encryption

Encryption is performed using a symmetric key algorithm known as Data Encryption Standard (DES) or its stronger cousin, Triple DES (3DES). Symmetric key algorithm means that a single key is used to encrypt as well as decrypt data. Although the keys for the incoming and outgoing IPsec SAs on a given peer are different, the key used by the ...