Encapsulation Security Payload (ESP) provides confidentiality, authentication, integrity, and can offer anti-replay as well. How does the ESP protocol provide proper confidentiality of the IP packets? It does this by simply applying encryption at the IP packet layer.

The main benefit of using the ESP protocol is its ability to provide data confidentiality (encryption) to the datagrams passing across the IPSec VPN tunnel:

The ESP protocol uses two encryption algorithms, these are the Data Encryption Standard and Triple Data Encryption Standard.

Data Encryption Standard:

• Symmetric encryption algorithm
• Uses block cipher, each block is 64-bit
• Encryption key is 56-bit long
• Due to the bit size of the encryption key, it is considered to be insecure

Triple Data Encryption Standard:

• Symmetric encryption algorithm
• Just as DES, encrypts 64-bit blocks of data at a time
• The length of the encryption key is also 56-bit
• Unlike DES, which encrypts a 64-bit block of data only once using the 56-bit key, 3DES encrypts the block of data three times using an independent 56-bit key