Data commit

Task/Bifid-cipher/Julia/bifid-cipher.julia

@@ -0,0 +1,25 @@
+polybius(text) = Char.(reshape(Int.(collect(text)), isqrt(length(text)), :)')
+
+function encrypt(message, poly)
+    positions = [findall(==(c), poly)[1] for c in message]
+    numbers = vcat([c[1] for c in positions], [c[2] for c in positions])
+    return String([poly[numbers[i], numbers[i+1]] for i in 1:2:length(numbers)-1])
+end
+
+function decrypt(message, poly)
+   n = length(message)
+   positions = [findall(==(c), poly)[1] for c in message]
+   numbers = reduce(vcat, [[c[1], c[2]] for c in positions])
+   return String([poly[numbers[i], numbers[i+n]] for i in 1:n])
+end
+
+
+for (key, text) in [("ABCDEFGHIKLMNOPQRSTUVWXYZ", "ATTACKATDAWN"), ("BGWKZQPNDSIOAXEFCLUMTHYVR", "FLEEATONCE"),
+   ([' '; '.'; 'A':'Z'; 'a':'z'; '0':'9'], "The invasion will start on the first of January 2023.")]
+    poly = polybius(key)
+    encrypted = encrypt(text, poly)
+    decrypted = decrypt(encrypted, poly)
+    println("Using polybius:")
+    display(poly)
+    println("\n  Message: $text\n    Encrypted: $encrypted\n    Decrypted: $decrypted\n\n")
+end