advertisement

Example 6 Continuation of Example 5 LPOFE MYFSO KVKIZ GWVJR VNUEK BAQWV ZFLWS BJMLH DTEHF LKEKB GAVPU JKQMA SBAEW AGAVA IESER FUITO WCYRV BUQWB KEEQT RLPKX WGCBJ LRRFO ZUSVJ XWGCB JLAFW LOALP KIAOK AWZKP AXNRJ was enciphered with a Vigenere cipher. Here is a picture of the four cosets mapped against the English Scrawl Here is coset 1 with 0 shift Here is coset 1 with a shift right of 8 or Left 18 Since 18 mod 26 is the inverse of 8 Mod 26 the letter we seek is the letter S. This is the first letter of the keyword. Here is the second coset with 0 shift. And here is the second coset with what appears as the best alignment. This time the alignment is not so obvious. However, notice how well the infrequent letters match (J, K, Q, X, and Z) and all the vowels have some probability. We see a shift right of 18 with inverse of 8. 8 Mod 26 gives the letter I. For the third coset the zero shift is: The best alignment comes with a shift right of 20 or left of 6. 6 mod 26 gives letter G. For the fourth coset with zero shift: And a shift right of 13 or left of 13 gives N as the fourth letter. The keyword is SIGN. Let’s try it. THISMESSAGEISATTENDEDFORSTUDENTSTOMOREFULLYUNDERSTANDHOWSIGNATURESANDSC RAWLSCANBEUSEDTODETERMINETHEKEYWORDLENGTHANDKEYWORDUSEDINTHEVIGENERECI PHER Or THIS MESSAGE IS ATTENDED FOR STUDENTS TO MORE FULLY UNDERSTAND HOW SIGNATURES AND SCRAWLS CAN BE USED TO DETERMINE THE KEYWORD LENGTH AND KEYWORD USED IN THE VIGENERE CIPHER. I used Vigenere Cipher program, not the Vigenere Decipher Program.