HP 3600 v2 Series Security Configuration Manual page 274

Figure 99 Encapsulation by security protocols in different modes
Authentication algorithms and encryption algorithms
Authentication algorithms
1.
IPsec uses hash algorithms to perform authentication. A hash algorithm produces a fixed-length digest for
an arbitrary-length message. IPsec peers respectively calculate message digests for each packet. If the
resulting digests are identical, the packet is considered intact.
IPsec supports the following hash algorithms for authentication:
MD5, which takes as input a message of arbitrary length and produces a 128-bit message digest.
•
• SHA- 1 , which takes as input a message of a maximum length less than the 64th power of 2 in bits
and produces a 160-bit message digest.
Compared with SHA- 1 , MD5 is faster but less secure.
Encryption algorithms
2.
IPsec mainly uses symmetric encryption algorithms, which encrypt and decrypt data by using the same
keys. The following encryption algorithms are available for IPsec on the switch:
• Data Encryption Standard (DES), which encrypts a 64-bit plain text block with a 56-bit key. DES is
the least secure but the fastest algorithm. It is sufficient for general security requirements.
Triple DES (3DES), which encrypts plain text data with three 56-bit DES keys. The key length totals
•
up to 168 bits. It provides moderate security strength and is slower than DES.
Advanced Encryption Standard (AES), which encrypts plain text data with a 128-bit, 192-bit, or
•
256-bit key. AES provides the highest security strength and is slower than 3DES.
IPsec SA setup modes
There are two IPsec SA setup modes:
• Manual mode. In this mode, you manually configure and maintain all SA settings. Advanced
features like periodical key update are not available. However, this mode implements IPsec
independently of IKE.
ISAKMP mode. In this mode, IKE automatically negotiates and maintains IPsec SAs for IPsec.
•
If the number of IPsec tunnels in your network is small, use the manual mode. If the number of IPsec
tunnels is large, use the ISAKMP mode.
IPsec tunnel
An IPsec tunnel is a bidirectional channel created between two peers. An IPsec tunnel comprises one or
more pairs of SAs.
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