60 lines
1.9 KiB
Text
60 lines
1.9 KiB
Text
function playfair(key, txt, isencode=true, from = "J", to = "")
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to = (to == "" && from == "J") ? "I" : to
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function canonical(s, dup_toX=true)
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s = replace(replace(uppercase(s), from => to), r"[^A-Z]" => "")
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a, dupcount = [c for c in s], 0
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for i in 1:2:length(a)-1
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if s[i] == s[i + 1]
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dup_toX && splice!(a, i+1+dupcount:i+dupcount, 'X')
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dupcount += 1
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end
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end
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s = String(a)
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return isodd(length(s)) ? s * "X" : s
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end
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# Translate key into an encoding 5x5 translation matrix.
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keyletters = unique([c for c in canonical(key * "ABCDEFGHIJKLMNOPQRSTUVWXYZ", false)])
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m = Char.((reshape(UInt8.(keyletters[1:25]), 5, 5)'))
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# encod is a dictionary of letter pairs for encoding.
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encod = Dict()
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# Map pairs in same row or same column of matrix m.
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for i in 1:5, j in 1:5, k in 1:5
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if j != k
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encod[m[i, j] * m[i, k]] = m[i, mod1(j + 1, 5)] * m[i, mod1(k + 1, 5)]
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end
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if i != k
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encod[m[i, j] * m[k, j]] = m[mod1(i + 1, 5), j] * m[mod1(k + 1, 5), j]
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end
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# Map pairs not on same row or same column.
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for l in 1:5
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if i != k && j != l
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encod[m[i, j] * m[k, l]] = m[i, l] * m[k, j]
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end
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end
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end
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# Get array of pairs of letters from text.
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canontxt = canonical(txt)
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letterpairs = [canontxt[i:i+1] for i in 1:2:length(canontxt)-1]
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if isencode
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# Encode text
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return join([encod[pair] for pair in letterpairs], " ")
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else
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# Decode text
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decod = Dict((v, k) for (k, v) in encod)
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return join([decod[pair] for pair in letterpairs], " ")
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end
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end
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orig = "Hide the gold in...the TREESTUMP!!!"
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println("Original: ", orig)
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encoded = playfair("Playfair example", orig)
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println("Encoded: ", encoded)
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println("Decoded: ", playfair("Playfair example", encoded, false))
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