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Pupil Text MEP: Codes and Ciphers, UNIT 11 Transposition 11 Transposition One method of encrypting messages is called transposition. A message, for example THIS IS A MESSAGE. HI is written across the rows in a grid: TH 1 To obtain the encrypted message, simply read down the columns: TTEGHSSELASHSMA To decrypt the message, do the reverse: write down the columns and read across the rows The security of this system lies in having to know the size and shape of the grid Example 1 You intercept the following message ASNEFOELBCVYNAWEEEOONASRNUTIYIEIDMT a) How many letters are there? b What possibilities are there for the shape of the grid? c) Use the information from (a) and (b) to unscramble the message Solution a) 35 letters b) 5 rows by 7 columns or 7 rows by 5 columns c) 7rows by 5 columns gives the grid: Reading along the ro ws, the messag e is ALWAYS BE SINCERE EVEN IF YOU DO NOT MEAN IT E ANIT Pupil Text MEP: Codes and Ciphers, UNIT 11 Transposition 11 Transposition One method of encrypting messages is called transposition. A message, for example THIS IS A MESSAGE. HI is written across the rows in a grid: TH 1 To obtain the encrypted message, simply read down the columns: TTEGHSSELASHSMA To decrypt the message, do the reverse: write down the columns and read across the rows The security of this system lies in having to know the size and shape of the grid Example 1 You intercept the following message ASNEFOELBCVYNAWEEEOONASRNUTIYIEIDMT a) How many letters are there? b What possibilities are there for the shape of the grid? c) Use the information from (a) and (b) to unscramble the message Solution a) 35 letters b) 5 rows by 7 columns or 7 rows by 5 columns c) 7rows by 5 columns gives the grid: Reading along the ro ws, the messag e is ALWAYS BE SINCERE EVEN IF YOU DO NOT MEAN IT E ANIT