Cryptography RSA - How to choose a public key
I need to choose a public key for a simple example where I use as alphabet, on the 0-th position the "_" character and from 1 to 27 the English alphabet (A-Z).

    _ABCDEF...Z

The theory says that the plain text is group of k letters and the cipher text is groups of l letters (this relation must also hold:  27^k <n < 27^l).
I choose  k=2 and l=3 but I also have  to choose a public Key: K_E = (n,e). How can i choose this pair of numbers ?(I also have an example K_E= (1643,67))
What those numbers represent?

Cryptography RSA - How to choose a public key
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I need to choose a public key for a simple example where I use as alphabet, on the 0-th position the "_" character and from 1 to 27 the English alphabet (A-Z).

    _ABCDEF...Z

The theory says that the plain text is group of k letters and the cipher text is groups of l letters (this relation must also hold:  27^k <n < 27^l).
I choose  k=2 and l=3 but I also have  to choose a public Key: K_E = (n,e). How can i choose this pair of numbers ?(I also have an example K_E= (1643,67))
What those numbers represent?
