D-Link DFL-1000 [77/168] About perfect forward secrecy pfs

D-Link DFL-1000 [77/168] About perfect forward secrecy pfs
DFL-1000 User Manual
7
7
Adding an AutoIKE key VPN tunnel
About the P2 proposal
During tunnel negotiation, the VPN gateways negotiate to select a common algorithm for data
communication. When you select algorithms for the P2 proposal, you are selecting the algorithms that the
DFL-1000 NPG proposes during phase 2 negotiation. For phase 2 to be completed successfully, each
VPN gateway must have at least one encryption and one authentication algorithm in common.
Select DES to propose to encrypt packets using DES encryption.
Select 3DES to propose to encrypt packets using triple-DES encryption.
Select MD5 to propose to use MD5 authentication.
Select SHA1 to propose to use SHA1 authentication.
Select NULL to propose that the VPN packets not be encrypted or that a hash is not made for
authentication.
About replay detection
IPSec tunnels can be vulnerable to replay attacks. A replay attack occurs when an unauthorized party
intercepts a series of IPSec packets and replays them back into the tunnel. An attacker can use this
technique to cause a denial of service (DoS) attack by flooding the tunnel with packets. An attacker could
also change and then replay intercepted packets to attempt to gain entry to a trusted network.
Enable replay detection to check the sequence number of every IPSec packet to see if it has previously
been received. If packets arrive out of sequence, the DFL-1000 NPG discards them.
The DFL-1000 NPG sends an alert email when replay detection detects a replay packet. To receive the
alert email, you must configure alert email and select "Enable alert email for critical firewall/VPN events or
violations". For information about alert email, see Configuring alert email
.
About perfect forward secrecy (PFS)
Perfect forward secrecy (PFS) improves the security of a VPN tunnel by making sure that each key
created during phase 2 is not related to the keys created during phase 1 or to other keys created during
phase 2. PFS might reduce performance because it forces a new Diffie-Hellman key exchange when the
phase 2 tunnel starts and whenever the keylife ends and a new key must be generated. As a result, using
PFS might cause minor delays during key generation.

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