Generate the public key and encode the plain text

Question

Let the alphabet be identified with $0,... 25$. In order to decrypt a plain text via RSA, we have prime numbers $p=53$ and $q=13$. Additionally we have $e=11$. Generate the public key and encode the plain text: GEDULD

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$p=53, q=13$

$N=p \cdot q = 689$

$r=(p-1) \cdot (q-1)=624$

We have $e=11$ so the public key is $(11,624)$?

Is this correct? But how to do the encryption with the word? I have no idea :s

Answer 1

The public key appears to be $(e, N) = (11, 689)$, but you give us a notation without explanation, so perhaps $e$ is meant to be the decrypting exponent, so you have to calculate the encrypting exponent via a gcd calculation, who knows?

Encryption depends on whether you encrypt one letter at a time, or two at a time, as you might be able to do here, as $26^2 < 689$. Again, you only know, and this depends also on the way you pack two letters in a single number. We cannot possibly know until you tell us.