Data commit

Task/Substitution-cipher/Nim/substitution-cipher.nim

@@ -0,0 +1,29 @@
+import sequtils, strutils
+
+proc encrypt(key: seq[char]; msg: string): string =
+  result.setLen(msg.len)
+  for i, c in msg:
+    result[i] = key[ord(c) - 32]
+
+proc decrypt(key: seq[char]; msg: string): string =
+  result.setLen(msg.len)
+  for i, c in msg:
+    result[i] = chr(key.find(c) + 32)
+
+when isMainModule:
+
+  import random
+  randomize()
+
+  # Build a random key.
+  var key = toSeq(32..126).mapIt(chr(it))   # All printable characters.
+  key.shuffle()
+
+  const Message = "The quick brown fox jumps over the lazy dog, who barks VERY loudly!"
+  let encrypted = key.encrypt(Message)
+  let decrypted = key.decrypt(encrypted)
+
+  echo "Key =       “$#”" % key.join()
+  echo "Message =   “$#”" % Message
+  echo "Encrypted = “$#”" % encrypted
+  echo "Decrypted = “$#”" % decrypted