Cipher decoding

Question

Ok, so as part of a challenge I've been trying to work out a cipher for the following string... r33z://sB.83swq.myw/5s/tzEx9tkzGSI/wy5sozy23o1.tzq?5=EpBGoFnm

It's pretty clearly a "fairly" simple character shift of +10 from the original, which turns r33z into http and wy5sozy23o1.tzq into movieposter.jpg. What I can't work out is the REST of the character set, and where it wraps. I tried doing all caps alphabet then all lowercase alphabet then numbers, shift 10 so the key would look like...

ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz01234567890 KLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz01234567890ABCDEFGHIJ

But this turns up a pretty strange URL aside from the obvious correct spots, that doesn't link to anything. Any thoughts?

And as a note, so I don't get given a hard time about it. The challenge says I can use "all the tools at my disposal," and I consider stackoverflow a very valuable tool ;)

Answer 1

This seems to work:

echo 'r33z://sB.83swq.myw/5s/tzEx9tkzGSI/wy5sozy23o1.tzq?5=EpBGoFnm' |\
    tr 'A-Za-z0-9' '0-9A-Za-z'