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Communications Security

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by

Koy Lapitan

on 22 February 2011

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Transcript of Communications Security

Communication Security deals with methods of protecting information while it is being transmitted. Communication Security Cryptography Crypography is the conversion of data into a
secret code over a public network. Original Msg
(Plaintext) Encoded Msg
(Ciphertext) Encryption Algorithm
(Cipher) Cipher is exchanged secretly
between sender and receiver. In classical cryptography, there is a message,
a sender, and a receiver. The message may be intercepted by a hostile person. The process of converting plaintext to cipher text is called encryption while the process of recovering plaintext from cipher text is called decryption. A Simple Encryption Algorithm Let the letters of the alphabet be represented
as two digit numbers from A=00 to z=25.

H E L L O
07 04 11 11 14

We may set as keys the position of the letter in the text.
H E L L O
00 01 02 03 04 A Simple Encryption Algorithm Add the plaintext to the encryption key, using modulo 26
arithmetic (if the sum of any two numbers is 26 or greater, then
subtract 26 from it).

H E L L O
07 04 11 11 14
+
00 01 02 03 04
=
07 05 13 14 18

0705131418 = HELLO
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