Section3

Section3 - LIGN 17 Section 3 – Friday, Jan 28th...

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Unformatted text preview: LIGN 17 Section 3 – Friday, Jan 28th and Tuesday, Feb 1, 2011 1 – One ­Time Pad Cipher What is the following message? I have enciphered it using a one ­time ­pad. N M Z Q R S 2 – Two ­Time Pad Cipher I just enciphered the following two messages using the same One ­Time Pad cipher. Oops. Now you can break it…. Message 1: Key M O M X S V Q K Q E D D Y O W U V Z L M L R L W R B I Z P J B K D A G L C Z Message CipherText Message 2: Ciphertext Message M O Q K W I Q J E G P R G D W G L S B Y I H E Q R G I 3 – Binary Numbers 1  ­ Conversion Convert from Decimal to Binary: 573 = ___________________________________ 101 = ___________________________________ Convert from Binary to Decimal: 1111001 = ________________________ 10101010101 = ______________________ Useful Powers of Two Chart: 213 8192 212 4096 211 2048 210 1024 29 512 4 – Binary Numbers 2 – Addition 111011010 + 101010101 5 – Binary Numbers 3 – Multiplication 111 x 101 28 256 27 128 26 64 25 32 24 16 23 8 22 4 21 2 20 1 6 – Binary Numbers 3 – XOR Encryption Rule: Cipher Text = 0 If both digits are the same in Key and Message; 1 if different Key 1 Message 0 Ciphertext 1 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 1 1 1 0 0 1 Key 0 Message Ciphertext 1 0 1 0 0 1 0 0 1 0 1 0 0 1 1 0 0 0 0 0 1 1 0 0 0 0 1 0 0 1 0 Key Message 0 Ciphertext 1 1 1 0 1 1 0 0 1 1 1 0 1 1 0 0 1 1 1 0 1 1 0 0 1 1 1 0 1 1 0 7 – Modular Arithmetic 9 (mod 15) = 44 (mod 2) = 44 (mod 3) = 83 (mod 7) = 152 (mod 3) = ...
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This note was uploaded on 09/15/2011 for the course LIGN 17 taught by Professor Kehler during the Winter '08 term at UCSD.

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