added rail fence cipher

rail-fence-cipher.py

@@ -0,0 +1,58 @@
+def encrypt(clearText, key):
+    result = ""
+    matrix = [["" for x in range(len(clearText))] for y in range(key)]
+    increment = 1
+    row = 0
+    col = 0
+    for c in clearText:
+        if row + increment < 0 or row + increment >= len(matrix):
+            increment = increment * -1
+        matrix[row][col] = c
+        row += increment
+        col += 1
+    for mlist in matrix:
+        result += "".join(mlist)
+    return result
+
+
+def decrypt(cipherText, key):
+    result = ""
+    matrix = [["" for x in range(len(cipherText))] for y in range(key)]
+    idx = 0
+    increment = 1
+    for selectedRow in range(0, len(matrix)):
+        row = 0
+        for col in range(0, len(matrix[row])):
+            if row + increment < 0 or row + increment >= len(matrix):
+                increment = increment * -1
+            if row == selectedRow:
+                matrix[row][col] += cipherText[idx]
+                idx += 1
+            row += increment
+    matrix = transpose(matrix)
+    for klist in matrix:
+        result += "".join(klist)
+    return result
+
+
+def transpose(m):
+    result = [[0 for y in range(len(m))] for x in range(len(m[0]))]
+    for i in enumerate(m):
+        for j in enumerate(m[0]):
+            result[j][i] = m[i][j]
+    return result
+
+
+def main():
+    clearText = "i am the king"
+    print("Original Text: " + clearText)
+    key = 3
+    cipherText = encrypt(clearText, key)
+    print("Encrypted Text: {0}".format(cipherText))
+    decipherText = decrypt(cipherText, key)
+    print("Decrypted Text: {0}".format(decipherText))
+    return
+
+
+if __name__ == '__main__':
+    main()