Playfair cipher: Difference between revisions

=={{header|Julia}}==

<lang julia>function playfair(key, txt, isencode=true, from = "J", to = "")

to = (to == "" && from == "J") ? "I" : to

function canonical(s)

s = replace(replace(uppercase(s), from => to), r"[^A-Z]" => "")

a = [c for c in s]

for i in 1:2:length(a)-1

if a[i] == a[i + 1]

a[i + 1] = 'X'

end

end

s = String(a)

return isodd(length(s)) ? s * "X" : s

end

# Translate key into an encoding 5x5 translation matrix.

keyletters = unique([c for c in canonical(key * "ABCDEFGHIJKLMNOPQRSTUVWXYZ")])

m = reshape(keyletters[1:25], 5, 5)

# encod is a dictionary of letter pairs for encoding.

encod = Dict()

# Map pairs in same row of matrix m.

for i in 1:5, j in 1:5, k in 1:5

if j != k

encod[m[i, j] * m[i, k]] = m[i, mod1(j + 1, 5)] * m[i, mod1(k + 1, 5)]

end

end

# Map pairs in same column of matrix m.

for j in 1:5, i in 1:5, k in 1:5

if i != k

encod[m[i, j] * m[k, j]] = m[mod1(i + 1, 5), j] * m[mod1(k + 1, 5), j]

end

end

# Map pairs not on same row or same column.

for (i1, j1, i2, j2) in [(a, b, c, d) for a in 1:5, b in 1:5, c in 1:5, d in 1:5]

if i1 != i2 && j1 != j2

encod[m[i1, j1] * m[i2, j2]] = m[i1, j2] * m[i2, j1]

encod[m[i2, j2] * m[i1, j1]] = m[i2, j1] * m[i1, j2]

end

end

# Get array of pairs of letters from text.

canontxt = replace(canonical(txt), r"[^A-Z]" => "")

letterpairs = map(x -> canontxt[x], findall(r"(.)(?:(?!\1)(.))?", canontxt))

if isencode

# Encode text

return join([encod[pair] for pair in letterpairs], " ")

else

# Decode text

decod = Dict((v, k) for (k, v) in encod)

return join([decod[pair] for pair in letterpairs], " ")

end

end

orig = "Hide the gold in...the TREESTUMP!!!"

println("Original: ", orig)

encoded = playfair("Playfair example", orig)

println("Encoded: ", encoded)

println("Decoded: ", playfair("Playfair example", encoded, false))

</lang>{{out}}

<pre>

Original: Hide the gold in...the TREESTUMP!!!

Encoded: MB OD BZ DX AN EB UK MD IU XM ZK RZ IY

Decoded: HI DE TH EG OL DI NT HE TR EX ST UM PX

</pre>