In Figure 8-10, someone wants to send a ?¬?nancial document across the Internet. At the local
end, the document is combined with a key and run through an encryption algorithm. The
output is undecipherable cipher text. The cipher text is then sent through the Internet. At the
remote end, the message is recombined with a key and sent back through the encryption
algorithm. The output is the original ?¬?nancial document.
The degree of security depends on the length of the key of the encryption algorithm. The
time that it takes to process all the possibilities is a function of the computing power of the
computer. Therefore, the shorter the key, the easier it is to break. Figure 8-11 shows the role
of the key in the process.
Encryption
Algorithm
Internet
Hmmm...
I cannot read a thing.
Encryption
Algorithm
Pay to Terry Smith $100.00
One Hundred and xx/100 Dollars
Pay to Terry Smith $100.00
One Hundred and xx/100 Dollars
4ehIDx67NMop9eR
U78IOPotVBn45TR
4ehIDx67NMop9eR
U78IOPotVBn45TR
310 Chapter 8: Extending the Network into the WAN
Figure 8-11 Encryption Key
Encryption algorithms such as DES and 3DES require a symmetric shared secret key to
perform encryption and decryption.
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