Reply To: Challenge 8B – Hints
I’m also very stuck and haven’t come close to cracking it yet, so don’t read anything into what I’m saying; I’m just trying to share ideas.
Assuming that it is derived from some kind of 5*5 Polybius Square that is read as two numbers at a time (maybe someone could confirm), it can be re-written as a substitution cipher. For example, the first part of the ciphertext would go from ‘143351’ to ‘DMU’ when put directly into the square. If you repeat this for the whole ciphertext, you end up with some other ciphertext that is easier to work with because it is in ASCII characters rather than pairs of numbers.
However, what you do from here (if this is even the correct first step) is beyond me. If you have done Part A (I haven’t), maybe try the same process for that.
It doesn’t seem to be any kind of monoalphabetic substitution as the IoC is two low. Again, this is all purely speculation; please do correct me if I am barking up the wrong tree.