So bored that just wrote a oneliner for deciphering (or more like brute forcing) substitution cipher.

One line substitution cipher decipherer

# Works on English alphabet with capital letters.

# Code with example usage
ruby -e "(1..25).each {|i| puts ARGV[0].chars.map {|e| Hash[('A'..'Z').zip(0..25)].invert[(Hash[('A'..'Z').zip(0..25)][e] + i) % 26]}.join('') + %Q|\n\n|}" ESLRPPAKPPFAUWPPKGPPOWPPSJWPPFAUW

# Output

FTMSQQBLQQGBVXQQLHQQPXQQTKXQQGBVX

GUNTRRCMRRHCWYRRMIRRQYRRULYRRHCWY

HVOUSSDNSSIDXZSSNJSSRZSSVMZSSIDXZ

IWPVTTEOTTJEYATTOKTTSATTWNATTJEYA

JXQWUUFPUUKFZBUUPLUUTBUUXOBUUKFZB

KYRXVVGQVVLGACVVQMVVUCVVYPCVVLGAC

LZSYWWHRWWMHBDWWRNWWVDWWZQDWWMHBD

MATZXXISXXNICEXXSOXXWEXXAREXXNICE   # <-- This little fella.

NBUAYYJTYYOJDFYYTPYYXFYYBSFYYOJDF

OCVBZZKUZZPKEGZZUQZZYGZZCTGZZPKEG

PDWCAALVAAQLFHAAVRAAZHAADUHAAQLFH

QEXDBBMWBBRMGIBBWSBBAIBBEVIBBRMGI

RFYECCNXCCSNHJCCXTCCBJCCFWJCCSNHJ

SGZFDDOYDDTOIKDDYUDDCKDDGXKDDTOIK

THAGEEPZEEUPJLEEZVEEDLEEHYLEEUPJL

UIBHFFQAFFVQKMFFAWFFEMFFIZMFFVQKM

VJCIGGRBGGWRLNGGBXGGFNGGJANGGWRLN

WKDJHHSCHHXSMOHHCYHHGOHHKBOHHXSMO

XLEKIITDIIYTNPIIDZIIHPIILCPIIYTNP

YMFLJJUEJJZUOQJJEAJJIQJJMDQJJZUOQ

ZNGMKKVFKKAVPRKKFBKKJRKKNERKKAVPR

AOHNLLWGLLBWQSLLGCLLKSLLOFSLLBWQS

BPIOMMXHMMCXRTMMHDMMLTMMPGTMMCXRT

CQJPNNYINNDYSUNNIENNMUNNQHUNNDYSU

DRKQOOZJOOEZTVOOJFOONVOORIVOOEZTV