Introduction to Cryptography

2. The probabilities (or frequencies) of the 26 letters of the English alphabet in English text are as follows.

Letter A B C D E F G H I

Prob. .082 .015 .028 .043 .127 .022 .020 .061 .070

Letter J K L M N O P Q R

Prob. .002 .008 .040 .024 .067 .075 .019 .001 .060

Letter S T U V W X Y Z

Prob. .063 .091 .028 .010 .023 .001 .020 .001

Using this information, decrypt the following ciphertext which was encrypted using a Shift Cipher:

RUNJAWNMQXFCXLJULDUJCNCQNJVXDWCXOYJYNAWNNMNMO XAJAXXVFQNWRFJBJCBLQXXUHXDVDUCRYUHCQNBZDJANOXXC JPNXOCQNFJUUBKHCQNLDKRLLXWCNWCBXOCQNOUXXAJWMLN RURWPLXVKRWNMJWMMXDKUNRCHXDCQNWJUUXFQJUOCQNCX CJUOXAXYNWRWPBBDLQJBFRWMXFBJWMMXXABCQNWHXDJU UXFCQNXCQNAQJUOOXAVJCLQRWPCQNYJCCNAWCQNWHXDMXDKU NCQNFQXUNCQRWPJPJRWCXPRENJVJAPRWXONAAXAJWMCQNWH XDXAMNACQNYJYNA