Linksys BEFSX41 manual Encryption, Authentication, Key Management

Instant Broadband® Series

•Any - If you select Any for the Remote Security Gateway, as shown in Figure 7-19, the VPN device at the other end of the tunnel will accept a request from any IP address. The remote VPN device can be another Firewall Router, a VPN Server, or a computer with VPN client software that supports IPSec. If the remote user has an unknown or dynamic IP address (such as a professional on the road or a telecommuter using DHCP or PPPoE), then Any should be selected.

Figure 7-19

Encryption

Using Encryption also helps make your connection more secure. There are two different types of encryption: DES or 3DES (3DES is recommended because it is more secure). You may choose either of these, but it must be the same type of encryption that is being used by the VPN device at the other end of the tunnel. Or, you may choose not to encrypt by selecting Disable.

Authentication

Authentication acts as another level of security. There are two types of authen- tication: MD5 and SHA (SHA is recommended because it is more secure). As with encryption, either of these may be selected, provided that the VPN device at the other end of the tunnel is using the same type of authentication. Or, both ends of the tunnel may choose to Disable authentication.

EtherFast® Cable/DSL Firewall Router with 4-Port Switch/VPN Endpoint

Key Management

In order for any encryption to occur, the two ends of the tunnel must agree on the type of encryption and the way the data will be decrypted. This is done by sharing a “key” to the encryption code. Under Key Management, you may choose automatic or manual key management.

Automatic Key Management

Select Auto (IKE) and enter a series of numbers or letters in the Pre-shared Key field. Check the box next to PFS (Perfect Forward Secrecy) to ensure that the initial key exchange and IKE proposals are secure. In the example shown in Figure 7-20, the word MyTest is used. Based on this word, which MUST be entered at both ends of the tunnel if this method is used, a key is generated to scramble (encrypt) the data being transmitted over the tunnel, where it is unscrambled (decrypted). You may use any combination of up to 24 numbers or letters in this field. No special characters or spaces are allowed. In the Key Lifetime field, you may optionally select to have the key expire at the end of a time period of your choosing. Enter the number of seconds you’d like the key to be useful, or leave it blank for the key to last indefinitely.

Figure 7-20

Manual Key Management

Similarly, you may choose Manual keying, which allows you to generate the key yourself. Enter your key into the Encryption KEY field. Then enter an Authentication KEY into that field. These fields must both match the infor- mation that is being entered in the fields at the other end of the tunnel. The example in Figure 7-21 shows some sample entries for both the Encryption and Authentication Key fields. Up to 24 alphanumeric characters are allowed to create the Encryption Key. Up to 20 alphanumeric characters are allowed to create the Authentication Key.

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