No worries. Just to explain why it's done this way: often, example presentations of e.g. the Caesar cipher will operate only on uppercase alphabetic characters, and everything else is "passed through". But sometimes you might want to treat, say, punctuation or lowercase letters as being part of the "alphabet" the cipher uses. So the spec allows you to specify which characters will be encrypted and which won't.

cheers

Arran

Hi again,

Yes, sorry for not clarifying, the section that you mentioned is what I was referring to. My understanding is that we should encrypt and decrypt according to those range_low and range_high values, incorporating wraparound. I have since had a closer look at the brief and this seems to be the case.

Thank you