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Secondary Cipher Challenge Part 1

Age 11 to 16
Challenge Level Yellow starYellow star
  • Problem
  • Getting Started
  • Teachers' Resources

This is the start of a six-part challenge.

Can you get to the end and crack the final message?

The ciphers in this challenge use some of the techniques discussed in the problems Substitution Cipher and Transposition Cipher, so you may want to have a go at those first.

Each message when decrypted gives a small clue to how the next challenge has been encrypted, and gives you a keyword that allows you to access the next challenge.

Good luck!

Part 1

Ltaa sdct udg hdakxcv iwt uxghi du iwt CGXRW Hipvt Iwgtt pcs Udjg rxewtg rwpaatcvth! Iwxh inet du rxewtg xh rpaats p Rpthpg hwxui pcs xh cpbts puitg Yjaxjh Rpthpg, iwt Gdbpc Tbetgdg, lwd jhts xi id rdbbjcxrpit lxiw wxh vtctgpah.

Iwt htrdcs rxewtg rwpaatcvt lxaa jht p sxuutgtci btiwds du tcrgneixdc. Wtgt pgt hdbt ixeh id wtae ndj id hdakt xi:

Pgt iwtgt pcn hxcvat atiitgh? Lwpi bxvwi iwtn qt?

Pgt iwtgt pcn hwdgi ldgsh? Rpc ndj iwxcz du pcn hwdgi ldgsh iwpi pgt jhts duitc?

Pgt iwtgt pcn pedhigdewth? Lwpi ldgsh sd ndj zcdl iwpi rdcipxc pedhigdewth? Sdth iwpi vxkt ndj pcn wxcih pqdji iwt atiitgh iwpi bxvwi qt jhts?

Uxcpaan, ndj ctts id zcdl iwt ztnldgs id prrthh iwt htrdcs rwpaatcvt. Xi lph p rdas pcs vaddbn spn lwtc X lgdit iwxh egdqatb, hd X rwdht p qgxvwi pcs rwttguja ztnldgs: gpxcqdl.


If you want to work on a computer to solve the problem, you can download this cipher as a text file which doesn't contain any line breaks.

We have created a Cipher Challenge Toolkit with some tools to help you crack different types of code.

Once you've decrypted this message, you should have a keyword.

You can access Part 2 of the Cipher Challenge at http://nrich.maths.org/???
by replacing the ??? with the keyword.

Notes and Background

You may find the Plus article Cracking Codes a useful and interesting read before embarking on the Cipher Challenge.

You may also like

The Best Card Trick?

Time for a little mathemagic! Choose any five cards from a pack and show four of them to your partner. How can they work out the fifth?

Substitution Cipher

Find the frequency distribution for ordinary English, and use it to help you crack the code.

Secret Transmissions

How can Agent X transmit data on a faulty line and be sure that her message will get through?

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The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to embed rich mathematical tasks into everyday classroom practice.

NRICH is part of the family of activities in the Millennium Mathematics Project.

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