Do you have the brains for cybersecurity? By Mark Ward

Technology correspondent, BBC News Published duration 24 March 2016

image copyright Getty Images image caption The code crackers at Bletchley Park worked hard to discover how the Enigma machine scrambled messages

If you want to stop people reading your secret messages, use a code to conceal the meaning.

From ancient times to the present day, security, codes and puzzles have been intertwined, as have the people who have tried to crack those codes to read messages they were never meant to see.

During World War Two, the code-cracking centre at Bletchley Park was known to recruit people who were a dab hand at solving crosswords and other puzzles. The thinking was that success at those challenges demonstrated an ability that could aid attempts to crack German codes and ciphers.

In the modern day, the ability to work through a problem and decipher it is essential to anyone who works in cybersecurity, partly because a lot of what they do involves working out what is going on with less than perfect knowledge.

The puzzles below have been drawn up with the help of the team behind the UK's Cyber Security Challenge, which uses similar tests to find people who are good at problem solving who could be of use for attacking and defending computer networks.

They range in difficulty from simple to knotty and fiendish.

Good luck.

Challenge One

This first puzzle is pretty straightforward. You even get the key. Use it to decipher the questions and then choose the right answer.

Challenge Two

This time there is no key to help decipher this short string of numbers, so it is a bit harder. However, here is a hint - once deciphered the string will reveal the name of a famous maths code that uses numbers.

5 8 1 14 13 0 2 2 8 18 4 16 20 4 13 2 4

image copyright AP image caption There is a clue to the answer for Challenge Two in this photograph.

Challenge Three

Code-breaking was practised in Roman times: Julius Caesar was known to use a code to securely send messages to his armies. This message uses a type of cipher named after the general to conceal its meaning. When you crack it you will find out where he kept his armies.

X S K L V V O H H Y L H V

image copyright Nelson Almeida image caption It's no joke that Caesar used ciphers to conceal messages to his troops

Challenge Four

Now the puzzles get more tricky. This code does not use numbers and letters to hide what it says. Instead, it swaps those familiar characters for symbols. Once cracked, the following message reveals who famously made use of this type of enciphering and the name of the technique. Here is a hint: it requires a code that shares its name with a place where a smelly farm animal is kept.

Challenge Five

This one is a real step up in difficulty. It can probably be done by trial and error, but it will be quicker to work out the rules governing the substitution and apply them. The key to cracking the message is elementary and you may find it easier to sit at a table rather than a desk to crack it.

Breaking the cipher will reveal a question. The solution is the answer to that question.

81, 1, 68, 59, 68, 86, 53, 76, 105, 53, 24, 22, 89, 5, 57, 68, 77, 50, 89, 81, 85, 4, 113, 71, 95, 86, 47, 44, 45, 33, 11, 64, 99, 12, 63, 10, 73, 8, 87, 52, 67, 68, 24, 72, 63, 25, 77, 6, 13, 3, 68, 57, 63, 101, 99, 60, 43, 14, 76, 88, 64, 47, 7, 53, 50, 99, 66, 76, 60, 22, 1, 99, 5, 47, 62, 53, 106, 8, 9, 81, 2, 68, 53, 75, 89, 52, 8, 25, 77, 27, 28, 113, 42, 4, 63, 75, 34, 63, 71, 63, 27, 52, 88, 76, 11, 17, 8, 11, 26, 77, 32, 113, 45, 13, 52, 77, 76, 11, 14, 13, 11, 66, 44, 63, 6, 115, 44, 37, 77, 7, 31, 6, 67, 63, 42, 77, 17, 13, 57, 84, 45, 8, 15, 63, 86, 43, 77, 68, 62, 74, 68, 23, 63, 92, 14, 68, 66, 53, 22, 52, 8, 24, 44, 68, 13, 81, 63, 18, 17, 53, 46, 72, 68, 44, 83, 39, 92, 62, 77, 28, 31, 52, 67, 63, 53, 28, 77, 43, 53, 13, 3, 3, 68, 65, 43, 63, 45, 34, 8, 26, 73, 67, 63, 68, 3, 63, 42, 68, 60, 65, 21, 4, 92, 73, 52, 74, 8, 57, 68, 65, 43, 63, 44, 38, 20, 13, 10, 52, 5, 63, 92, 50, 68, 66, 74, 67, 13, 81, 33, 75, 68, 81, 80, 63, 70?

image copyright Science Photo Library image caption The appliance of science should help crack this message

Challenge Six

Good work if you have got this far. This final challenging set of puzzles has three parts; when each one is completed it will reveal a quote from a well-known work of literature, whose author loved intellectual games of all kinds. Can you find all three?

Bear in mind while you are working on these that each puzzle is not necessarily just a cipher - there are some computer science basics mixed in. Each one is designed to be solved independently so if one of the puzzles defeats you then move on. Here's one final clue: Alice fell down a rabbit hole and left clues so Bob could find her...

The BBC would like to thank Bryony Chinnery and the UK's Cyber Security Challenge for helping to draw up this set of coding challenges.