Basic Vpn Terms And Concepts - Dell SonicWALL GX250 Manual

Basic VPN Terms and Concepts

• VPN Tunnel
A VPN Tunnel is a term that describes a connection between two or more private
nodes or LANs over a public network, typically the Internet. Encryption is often
used to maintain the confidentiality of private data when traveling over the
Internet.
• Encryption
Encryption is a mathematical operation that transforms data from "clear text"
(something that a human or a program can interpret) to "cipher text" (something
that cannot be interpreted). Usually the mathematical operation requires that an
alphanumeric "key" be supplied along with the clear text. The key and clear text
are processed by the encryption operation, which leads to data scrambling that
makes encryption secure. Decryption is the opposite of encryption: it is a
mathematical operation that transforms cipher text to clear text.
• Key
A key is an alphanumeric string used by the encryption operation to transform clear
text into cipher text. A key is comprised of hexadecimal characters (0, 1, 2, 3, 4,
5, 6, 7, 8, 9, a, b, c, d, e, f). A valid key would be 1234567890abcdef. Keys used
in VPN communications can range in length, but are typically 16 or 32 characters.
The longer the key, the more difficult it is to break the encryption.
• Asymmetric vs. Symmetric Cryptography
Asymmetric and symmetric cryptography refer to the keys used to authenticate, or
encrypt and decrypt the data.
Asymmetric cryptography, or public key cryptography, uses two keys for
verification. Organizations, such as RSA Data Security and Verisign, support
asymmetric cryptography.
With symmetric cryptography, the same key is used to authenticate on both ends
of the VPN. Symmetric cryptography, or secret key cryptography, is usually faster
than asymmetric cryptography. Therefore symmetric algorithms are often used
when large quantities of data need to be exchanged. SonicWALL VPN uses
Symmetric Cryptography. As a result, the key on both ends of the VPN tunnel must
match exactly.
• Security Association (SA)
A Security Association is a group of security settings related to a specific VPN
tunnel. A Security Association groups together all the necessary settings needed to
create a VPN tunnel. Different SAs may be created to connect branch offices, allow
secure remote management, and pass unsupported traffic. All Security
Associations (SAs) require a specified Encryption Method, IPSec Gateway Address
and Destination Network Address. IKE includes a Shared Secret. Manual Keying
includes two SPIs and an Encryption and Authentication Key.
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