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The sixth hint for Challenge 10A


The sixth hint for Challenge 10A


If Jodie sent this message and signed it we will see the bigrams OD, IE at the end and these are represented by the vectors (14, 3) and (8, 4).

What we actually see are the letter pairs RU, MQ which correspond to the vectors (17,20) and (12,16), so the encryption works to give

14a+3b = 17


8a+4b =12


We can solve these four equations in four unknowns to get the encryption parameters. Try looking up solving systems of equations online, but be careful doing so in mod 26 arithmetic!

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