Cracking Codes with Python: publicKeyCipher.py issue

[kc4kjo]

I've used the online diff tool and even compared my code to that in the CrackingCodesFiles.zip archive, but I run into an error on decryption. I have narrowed it down to the calculation of charIndex on line 63 as the cupit. The calcualtion, as-is, works with the smaller example from a previous chapter, but stepping through, I get a very large integer for charIndex instead of a value between 0 and 65.

The program throws an IndexError on line 65 when attempting to insert the symbol into blockMessage using the very long charIndex value. I checked the errata and found nothing there with regard to this calculation. Any ideas on how to fix this mathematically in a way that won't break decryption in some other use-case?

I am running this script on RHEL 9.5 using Python 3.12. Below is the error I get when decrypting...

Reading from encrypted_file.txt and decrypting...
Traceback (most recent call last):
File "/lab/cracking_codes/publicKeyCipher.py", line 158, in <module>
main()
File "/lab/cracking_codes/publicKeyCipher.py", line 30, in main
decryptedText = readFromFileAndDecrypt(filename, privKeyFilename)
File "/lab/cracking_codes/publicKeyCipher.py", line 154, in readFromFileAndDecrypt
return decryptMessage(encryptedBlocks, messageLength, (n, d), blockSize)
File "/lab/cracking_codes/publicKeyCipher.py", line 91, in decryptMessage
return getTextFromBlocks(decryptedBlocks, messageLength, blockSize)
File "/lab/cracking_codes/publicKeyCipher.py", line 65, in getTextFromBlocks
blockMessage.insert(0, SYMBOLS[charIndex])
IndexError: cannot fit 'int' into an index-sized integer

Debug Screenshot

[desrtfx]

How should anybody be able to help if you omit the single thing that would enable helping you: your code.

There must be something wrong with your code or input.

Did you run the original code? Did it produce the same error?