ZyXEL P-793H User Guide - Page 173
Manual Key Setup
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Chapter 11 VPN Table 43 Security > VPN > Setup > Edit > Advanced Setup (continued) LABEL DESCRIPTION Encryption Algorithm This field is available when you select ESP in the Active Protocol field. Select DES, 3DES, AES or NULL from the drop-down list box. When you use one of these encryption algorithms for data communications, both the sending device and the receiving device must use the same secret key, which can be used to encrypt and decrypt the message or to generate and verify a message authentication code. The DES encryption algorithm uses a 56-bit key. Triple DES (3DES) is a variation on DES that uses a 168-bit key. As a result, 3DES is more secure than DES. It also requires more processing power, resulting in increased latency and decreased throughput. This implementation of AES uses a 128-bit key. AES is faster than 3DES. Authentication Algorithm SA Life Time (Seconds) Select NULL to set up a tunnel without encryption. When you select NULL, you do not enter an encryption key. Select SHA1 or MD5 from the drop-down list box. MD5 (Message Digest 5) and SHA1 (Secure Hash Algorithm) are hash algorithms used to authenticate packet data. The SHA1 algorithm is generally considered stronger than MD5, but is slower. Select MD5 for minimal security and SHA-1 for maximum security. Define the length of time before an IKE SA automatically renegotiates in this field. It may range from 60 to 3,000,000 seconds (almost 35 days). Encapsulation Perfect Forward Secrecy (PFS) Back Apply Cancel A short SA Life Time increases security by forcing the two VPN gateways to update the encryption and authentication keys. However, every time the VPN tunnel renegotiates, all users accessing remote resources are temporarily disconnected. Select Tunnel mode or Transport mode from the drop-down list box. Perfect Forward Secrecy (PFS) is disabled (NONE) by default in phase 2 IPSec SA setup. This allows faster IPSec setup, but is not so secure. Choose DH1 or DH2 from the drop-down list box to enable PFS. DH1 refers to Diffie-Hellman Group 1 a 768 bit random number. DH2 refers to Diffie-Hellman Group 2 a 1024 bit (1Kb) random number (more secure, yet slower). Click Back to return to the previous screen. Click Apply to save your changes back to the P-793H v2 and return to the VPN-IKE screen. Click Cancel to return to the VPN-IKE screen without saving your changes. 11.5 Manual Key Setup Manual key management is useful if you have problems with IKE key management. P-793H v2 User's Guide 173