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For instance I'm asked to decipher the following message:

2206 0755 0436 1165 1737 where I'm given the private key, $\ d=2437$ and with respect to modulo $\ n=2747$

I get

$\ 2206^{2437}$ $\cong$ $\ 617$ $\ $mod $\ 2747$

and proceeding so on for each block of 4 digits I get $\ 617, 404, 1908, 1306, 1823 $

but I'm unsure how to translate this into letters relating to the alphabet (ie A=0, B=1,.....,Z=25)

Any help appreciated.

Mike
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1 Answers1

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Hint: Each two digits correspond to a letter: $$ 617, 404, 1908, 1306, 1823 \to 06,17,04,04,19,08,13,06,18,23 \to G, R, \dots $$

lhf
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    I guessed. It turned out to be a word. But you need two digits to describe all letters, so it cannot be all one digit. – lhf Nov 16 '19 at 13:11
  • You can fit two two-digit numbers in $0,\ldots 25$ within $2747$ when concatenating, so it makes sense. Max is zz=2525. Bad encoding as aa =00 which is a fix point. That's why actual RSA does it differently (OAEP or PKCS 1.5 e.g.) – Henno Brandsma Nov 18 '19 at 07:24