## Decode this…

guvf zrffntr unf orra rapbqrq hfvat gur fvzcyr vqrn bs cynpvat gur yrggref bs gur nycunorg ebhaq n qehz naq ebgngvat rnpu yrggre 13 cynprf, fb n orpbzrf z. v’yy or hfvat vg gbzbeebj jvgu fghqragf nf n fvzcyr rkrepvfr. gur fghqragf jvyy unir gb

• jbex va cnvef
• hfr n gnoyr bs crepragntr serdhrapvrf bs gur yrggref va gur nycunorg naq n ovg bs pbzzba frafr gb qrpbqr gur zrffntr
• rapbqr n zrffntr naq fraq vg gb nabgure cnve guvf vf cercnengvba sbe fbzr jbex ba gur cflpubybtl bs pbzchgre unpxref.

### Did it work?

18th Oct: Well, the codebreaking activity went down quite well – the students were determined to solve the rather simpler rot13 message given. They had a table of the frequencies of letters in English words. I used this as an introduction to the hacker mind and why hackers use online communities so much. The logic was as follows…

• Work in pairs
• Try to find as many letters/words as you can (Scrabble?)
• (after 5 min) Share your information with other pairs
• Work as a class group of pairs to solve the problem
• Can you find a rule for the ‘substitution code’ being applied?
• How many bytes of information would it take to send someone details of the substitution rule? Less than a table of 26 letters and 26 coded letters (ie less than 52 bytes plus spaces)?

The feedback went along the lines of…

• How did you feel working on the puzzle?
• How did sharing the information from other pairs help?

Results with a mature day group were interesting: two of the pairs got a long way to solving the puzzle – they had about 10 words sorted – using frequency analysis and guesswork from the shape of the words.

When we pooled the information from the pairs, the combined result was much better and one member of a pair that had ‘switched off’ became re-engaged and spotted the rule (move letters 13 along)

The moral is obvious – Cognitive puzzle solving is hard but hackers can multiply their efforts by using online communities.