Codes and Ciphers

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Codes and Ciphers
By the end of this session you will be able to
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Solution
By the end of this session you will be able to

• Decode messages using different ciphers

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Round 1- Texting Challenge

• Examples
• 927
• WAS/WAR
• 2628
• BOAT/COAT
• 4483
• GIVE/HIVE

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Round 1- Texting Challenge
9428 36 968 2255 2 74337 9484 66 5347? 2
25683!
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Round 1- Texting Challenge
Solution 9428 36 968 2255 2 What do you call a
74337 9484 66 5347? sheep with no legs? 2
25683! A cloud!
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Round 2- Transposition Challenge

• Example
• Welcome to Leeds University
• welcometoleedsuniversity
• 24 letters long
• 64 or 212 or 38 or 212 or 124
• So write

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Round 2- Transposition Challenge

• Going the other way round
• ckatsoenaadekifepdlesbesr
• 25 letters 55
• So write

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Round 2- Transposition Challenge

• Example
• cbkhenlroreedwdtderlwowweaspirao
• 32 letters long
• 132 or 216 or 48
• So write

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Round 2- Transposition Challenge

• Challenge
• trmsimhlatsledld1owslo5nosegcg

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Round 2- Transposition Challenge
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Round 2- Transposition Challenge

• Challenge
• trmsimhlatsled1owslo5nosegcg
• Answer

t h e w o
r l d s s
m a l l e
s t d o g
i s 1 5 c
m l o n g
The worlds smallest dog is 15cm long
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Round 3- Pencil Code
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Round 3- Pencil Code

• Answer-
• This code was used 2500 years ago by the Spartans
  in Ancient Greece.

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Refreshment Break

• This would be a good time to try to earn some
  bonus points with the Number Phrase Round!

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Round 4- Binary Challenge

• Practise Questions
• 00010
• 11111
• 10011
• 00101

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Round 4- Binary Challenge
Answer Computers view everything as ones and
zeroes!
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Round 5- Error Checking Challenge
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• error_checking_example.doc

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Error Checking
1 0 1 1 1
0 1 0 1 0
1 0 1 0 1
0 1 1 1 1
0 1 1 1 1
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• Image from the 2006 Royal Institution Christmas
  Lectures

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Image from the 2006 Royal Institution Christmas
Lectures
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The Final!Frequency Analysis
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Other handy hints when cracking codes

• The most frequent two-letter words are OF, TO,
  IN, IT and IS
• The most frequent three letter words are THE,
  AND, FOR, ARE and BUT
• Half of all English words begin with A,O,S,T or W

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The Solution !

• The best code crackers wont give up and always
  want to find the answer. Often there is a reward
  for those who succeed.

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