Motorola SVG1501UE 用户手册

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10 • VPN Pages 

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Select one of the Diffie-Hellman groups: 768 bits, 1024 bits, or 
1536 bits. 

Diffie-Hellman is a cryptographic technique that uses public 
and private keys for encryption and decryption. The higher the 
number of bits, the more secure the encryption. Options: 
Group 1 (768 bits), Group 2 (1024 bits), or Group 5 (1536 bits). 

Secure the VPN connection between endpoints: DES, 3DES, 
AES-128, AES-192, or AES-256.  

Select any encryption but make the far endpoints match. 
Common encryption settings are 3DES and AES. 

Set Authentication, another level of security, to SHA or MD5  

Motorola recommends SHA because it is more secure but you 
can use either authentication provided the other end of the 
VPN tunnel uses the same method. 

Specify the lifetime of individual rotating keys. 

Enter the number of seconds for the key to last until a re-key 
negotiation between each endpoint is negotiated. The default 
setting is 28,800 seconds. 

A smaller lifetime is generally more secure, since it would give 
an attacker a smaller amount of time to try to crack the key, 
however key negotiation takes up bandwidth, so network 
throughput is sacrificed with small lifetimes. Entries are 
typically in the thousands or tens of thousands of seconds.