HandoutApr. 2007Cryptography A Lecture in CE Freshman Seminar Series: Ten Puzzling Problems in Computer Engineering

HandoutApr. 2007Cryptography Simple Substitution Ciphers Decipher the following text, which is a quotation from a famous scientist. Clue: Z stands for E “CEBA YUC YXSENM PDZ SERSESYZ, YXZ QESOZDMZ PEJ XQKPE MYQGSJSYA, PEJ S’K ECY MQDZ PLCQY YXZ RCDKZD.” PBLZDY ZSEMYZSE “CEBA YUC YXSENM PDZ SERSESYZ, YXZ QESOZDMZ PEJ XQKPE MYQGSJSYA, PEJ S’K ECY MQDZ PLCQY YXZ RCDKZD.” PBLZDY ZSEMYZSE “ E E E E E, E E E.” E E E ,

HandoutApr. 2007Cryptography

HandoutApr. 2007Cryptography Decoding a Key-Based Cipher A B C D E F G H I J K L M N O P Q R S T U V W X Y Z Agreed upon secret key: freshman __ __ __ __ __ __ __ Secret key: f r e s h m a n f r e s h m Sum: __ __ __ __ __ __ __ __ __ __ __ __ __ __ Modulo 26 sum: __ __ __ __ __ __ __ __ __ __ __ __ __ __ Cipher text: __ __ __ __ __ __ __ __ __ __ __ __ __ __ Decipher the coded message and provide a reply to it using the same key Message: B Y E L P E Y B Z I R S T Q Secret key: f r e s h m a n f r e s h m Difference: __ __ __ __ __ __ __ __ __ __ __ __ __ __ Modulo 26 diff.: __ __ __ __ __ __ __ __ __ __ __ __ __ __ Plain text: __ __ __ __ __ __ __ __ __ __ __ __ __ __ Reply: _ _ _ _ _ _ _ _ _ _ _ _ _ _