I need an array populated with characters and integer keys for each, and I want to, using this set, encode messages, and then decode them later on . Essentially I am trying to write RSA algorithm for this. However, the maths of it is what I am still kind of lost on. In order to encode, I would have to encode bits of the input string, and this after reading the corresponding key for each character, M.
Ciphertext=0 for i from 1 to length(message) do M:= ltable[message[i]] // Read the number that corresponds to the Character ciphertext:= ciphertext * ((M^encryptionkey) mod modfactor);//encode the returned number and add to ciphertext Loop next return ciphertext; //To Convert all the input message at once, and then encode I have this algorithm ** for i from 1 to length(message) do M:= ltable[message[i]]//get the number that corresponds to character ciphertext:= ciphertext * M;//perform operation to update Loop next return ((ciphertext^encryptionkey) mod modfactor);**
i.e Ciphertext = M^e mod n where C is the resulting ciphertext, e is my encryption key and modfactor is the product of my primes.
The code above spews out my input message in an encrypted form. However, when I am to decode to resulting ciphertext, I run into some problem reversing the operations above to get the exact message that was sent as input to my encryption program. Essentially given a String of length 100, I encrypt each character of the input string with the above, but to reverse/decode, I don't seem to be getting the same message.
cipher = cyphertext;
while cipher> 0 do
rest = (cipher ^decryptionkey) mod modfactor
message = concatenate(ntable[rest],message):
wrk = (cipher/rest)/modfactor
The code/algorithm above does not seem to work. Test primes used are p=263 and q=911, and encryptionkey= 27 How do I accomplish this please?