# You're reading: Posts Tagged: substitution cipher

### Competition: Cryptogram Puzzle

Author and mathematician Josh Holden has come up with a nice puzzle — so we’re posting it as a competition. If you think you can decrypt the message below, send in the decrypted message and a one- or two-sentence description of the mathematical principle behind the encryption key to root@aperiodical.com.  The first correct entry received will win a copy of Josh’s book, The Mathematics of Secrets.

The technical name for the “cryptograms” found in many newspapers and magazines is monoalphabetic monographic substitution ciphers — monographic meaning that they make substitutions one letter at a time and monoalphabetic meaning that the substitution rule is the same every time a given letter appears in the message.

Most often the easiest way to start solving these is to look at one-letter words which are usually “I” or “a”, then two-letter words, etc. If the breaks between the words are removed, then you might use the fact that in a typical English text the letter “e” will occur about 13% of the time, followed by “t” and “a” at 7-8% and others farther behind.

What then should we make of the following cryptogram?

YOFQX RGLQT GCQPB FFGQJ IQOFT SYVQH FSFQV FTYFC QJGQY OFRSQ YOSJG FQHOF GQYOF NQTSS REFCQ HRYOQ TQLSF TYQZS JHCQT VVFDW AFCQT WJBYQ YOFDQ TAAQV JSYVQ JIQAR YYAFQ WRSCV QTGCQ WFTVY VQTVQ HFAAQ TVQYO FQHOJ AFQMT ZXQJI QZTSC VQYOF QXGTE FQHTV QVYTG CRGLQ WFIJS FQYOF DQRGQ ZOTRG VQHRY OQTQV JACRF SQJGQ FTZOQ VRCFQ YJQLB TSCQO RDQTG CQGFT SQYOF QXRGL QHTVQ YOFQH ORYFQ STWWR YQHRY OQTQY SBDMF YQRGQ JGFQO TGCQT GCQTQ VZSJA AQJIQ MTSZO DFGYQ RGQYO FQJYO FS

The letter “Q” appears almost 20% of the time, followed by “F” at about 10%, and “Y” and “T” at about 8%. The original text is English (in fact it’s from a famous work of children’s literature) and it doesn’t have a particularly odd distribution of letters. Can you decrypt the message? For bonus points, can you figure out what is mathematically interesting about the encryption key?