To write this program, I needed to know how to write the algorithms for the Euler’s Totient, GCD, checking for prime numbers, multiplicative inverse, encryption, and decryption. I did not see this question when posting (swear i looked).The below program is an implementation of the famous RSA Algorithm. I didn't post this on crypto because it seems to be outside their scope since the issue isn't directly with the cryptography. I have looked at this post quite a bit and believe it probably would have helped me solve my problem if the author hadn't apparently deleted some of their comments.
My question is how am I supposed to convert these long values back to ascii? Or am I supposed to do some sort of translation before the decryption operation which wouldn't leave me with these longs? Note that I have tried reading the file in 64bits at a time, but that leaves me with 2 large longs that I still don't know how to convert. Which produces the following output: input as read from file: 6ëC= Str.append(mm_chr) #put in a list for easier viewing Print('input as read from file: '.format(input)) The resulting encrypted value(screenshot to preserve special chars): My plaintext that I am encrypting: this is a test! Trying to use chr() to convert these to ascii obviously fails with a OverflowError: Python int too large to convert to C long error.
This leaves me with a very large long, e.g. In my code I read in the encrypted file, convert it to hex and then perform the decrypt operation on each hex value. Since I have the actual private key, I am able to confirm that I have done this part correctly and have the right primes / private exponent. I am then attempting to walk through the exercise, taking the public key and deducing the private exponent from there. Openssl rsautl -encrypt -raw -inkey public_key.pem -pubin -in test.txt -out test.enc I am encrypting a file using openssl rsautl with the -raw padding option like so: I am intentionally using a weak RSA key (128bit) so that it can be factored and the private exponent deduced. The idea is that you are given an encrypted file and an RSA public key and have to decrypt the file. I am trying to build a module for a CTF I am planning.
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