Basic Vpn Terms And Concepts; Asymmetric Vs. Symmetric Cryptography - SonicWALL TELE3 SP Administrator's 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 typically consist of 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 have 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 of the settings necessary to create a VPN tunnel.
Different SAs can 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.
Page 158 SonicWALL TELE3 SP Administrator's Guide