DevonRevenge's decoding challenge #1: I scrambled a sentence can you decode it(with algorithm provided)

[devonrevenge]

my alphabet...char zeta[27]= {'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z',' '};

is that in the correct order? im dyslexic enough to never really be sure

[Catfish3]

Yes it is. Hmm...

Edit: works now.

[helios]

hamsterman: Good eye. I hadn't considered interactions between a and cipher. Actually, the same happens for cipher=3. This is because 3 is a divisor of 27. When cipher=9 it's even worse. All letters map to one of {0,9,18}.

So yeah. Bad idea to mix multiplication and modulo by a non-prime.

[Catfish3]

Hey devon, let's communicate (I'm using the same "cipher" and alphabet).

sgetrutymodhrudwgmhgv pmpjnqcfbmynyfnpqq

[devonrevenge]

henhmuuwhfsnvpywyddsusdtremxegymlfpvqccrudwgisravdpuo

[Catfish3]

wfihhqyyjoinxszggehrlfojlxwwaicdzvca

fcefqbtykfirhozblonsddpylptwevbmi atfiwpozgi opeodqk