Chaff n Winnow - Printable Version

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Welcome to Chaff n Winnow
Your goal is to decrypt the message, but unfortunately, you'll need to figure out whether a byte corresponding to a letter, are valid. If the byte is valid, then the letter makes up the secret message. 
There are rules to which bytes are valid but I won't tell you. You'll just have to write a message with a byte, and I'll tell you whether it's valid or not.

J  S  H  A  I  I  S  S  G  N  P  L  O  N  X  G  P  I  K  W  Z  K  E  D  F  M  O  G  L  S 
66 ec ff 2b fb 3c b5 65 bc 99 de 71 ac 7b ff e6 98 1e fc ba b4 c7 86 1a 16 cc 03 8a e2 01