WATAE TXLAL PDIBI MGTBU YBTMM FJBJW KBEIZ SGLZQ CCOCT XMQHM QSLFS
AOBFX QQRCK CJSME XFHLT GYSJN QEQUM FNPIZ ZMCWE PXQOD UIDLO SXLCV
CGIWI UIVYC HLYAE TKYKY RVOVZ FJWAR RCYCN SSJNN ADVZB BMQJQ UVGKC
UCPVN BGRZA EVOMF THBSK OZUYQ QDGUO FUIAT XOWPN QESJM MUHHU XBTMM
NYGYF YFNFH VIATB UOHPD QVJAT AEYLT MQTLE EXBTH MMYCT BDDAX
Determine what this cipher says, and the method of encryption, using the following hints:
- It is not a simple substitution cipher.
- Both the original plain text message and the encrypted message contain 270 characters (maybe with meaningless filler characters at the end).
- Only one rather simple method of encryption has been used.
- The encryption method is fairly robust. In other words, an error (while encrypting or decrypting) does not scramble the entire remaining message. Some very complicated ciphers have this problem.
- In the encrypted text, M and T appear most often, and R appears least often (I do not think these facts help at all).
- Both the original plain text and the encrypted message read from left to right.
- You might be able to guess the full text after determining only the first three words.
(In reply to
the actual decryption by Tristan)
Thanks Tristan... kudos for pointing that out!
That gave it to me...
The first has no predecessor and predecessor is all we need to encode the next letter.
First, each letter has a number associated with it A=0 through Z=25.
Encoding...
WETHEPEOPL
22 4 19 7 4 15 4 14 15 11
just add the value of the previously encoded letter and then mod 26 (subtract 26 if it is above 25).
So... encoded:
the first letter is 22 + previous letter (0) = 22, encoded = 'W'
the second letter is E=4, + 22 =26, MOD 26 = 0, ENCODED = 'A'
the third letter is T=19 + 0 =19, MOD 26 = 19, ENCODED = 'T'
the fourth letter is H=7 + 19 = 26, MOD 26 = 0, ENCODED = 'A'
the fifth letter is E=4, + 0 = 4, MOD 26 = 4, ENCODED = 'E'
the sixth letter is P=15, + 4 = 19, MOD 26 = 19, ENCODED = 'T'
the seventh letter is E=4, + 19 = 23, MOD 26 = 23, ENCODED = 'X'
the eight letter is O=14, + 23 = 37, MOD 26 = 11, ENCODED = 'L'
... and so on ...
I leave it as an exercise to the reader to reverse the process.
Thanks again, Tristan!
re: the actual decryption
