diff --git a/lc4.py b/lc4.py
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+#!/usr/bin/python2
+# -*- coding: utf-8 -*-
+# This software is hereby released into public domain. Use it wisely.
+# 
+# ElsieFour (LC4) and its enhancement LS47
+# version 2.7: 2018-02-13
+#
+# - Python script for LS47 originally written by Mirek Kratochvil (2017)
+#   See https://github.com/exaexa/ls47
+# - Python 3 port by Bernhard Esslinger / AK (Feb 2018)
+#   See www.mysterytwisterc3.org
+# - New options by CrypTool project (www.cryptool.org) (Feb 2018) in order to
+#   support both ciphers LC4 and LS47, both ways to deal with nonces, keyword
+#   usage for both LC4 and LS47, reading from file and commandline, and
+#   extended test outputs.
+# 
+# Sample calls:
+# - Using cipher LC4, enforced with option -6:
+# python lc4-ls47.py -6 -ws thisismysecretkey -es its_my_fathers_son_but_not_my_brother -v -nl 6
+# python lc4-ls47.py -6 -ws thisismysecretkey -ds q6xojffkncfyz#f5czs49#3mbsco#2iscvbnm#bymaf -v -nl 6
+# - Using cipher LS47, enforced with option -7:
+# python lc4-ls47.py -7 -ws s3cret_p4ssw0rd/31337 -ds y'zbvvs+d2,ky4sy?w(_wkz*7'90v:./s)kcz?mj+gyu8-'h(y,i+v,z+1ws -v -nl 10
+# python lc4-ls47.py -7 -ws s3cret_p4ssw0rd/31337 -ds y'zbvvs+d2,ky4sy?w(_wkz*7'90v:./s)kcz?mj+gyu8-'h(y,i+v,z+1ws -v -ns 8y(l._4ct'
+#
+
+
+from __future__ import print_function
+import sys
+import os
+import random
+import argparse
+
+
+version = "v2.7 (2018-02-13)"
+
+letters6 = "#_23456789abcdefghijklmnopqrstuvwxyz"
+letters7 = "_abcdefghijklmnopqrstuvwxyz.0123456789,-+*/:?!'()"
+
+
+def missing_letters(s,t):
+    return ''.join(sorted(set(c for c in s if c not in t)))
+
+
+def check_key(key):
+    illegal = missing_letters(key,letters)
+    missing = missing_letters(letters,key)
+    duplicates = ''.join(sorted(c for c in letters if key.count(c)>1))
+
+    errors = []
+    if illegal: errors.append( "Key contains illegal letters: '%s'" % illegal )
+    if missing: errors.append( "Key misses some letters: '%s'" % missing )
+    if duplicates: errors.append( "Key contains duplicate letters: '%s'" % duplicates )
+
+    if errors:
+        errors.append( "The key must be a permutation of the alphabet: %s" % letters )
+        raise ValueError("\n".join(errors))
+
+
+def check_nonce(nonce):
+    illegal = missing_letters(nonce,letters)
+    if illegal:
+        raise ValueError("Nonce contains illegal letters: '%s'" % illegal)
+
+
+def check_plaintext(s):
+    illegal = missing_letters(s,letters)
+    if illegal:
+        raise ValueError("Plaintext contains illegal letters: '%s'" % illegal)
+
+
+def check_ciphertext(s):
+    illegal = missing_letters(s,letters)
+    if illegal:
+        raise ValueError("Ciphertext contains illegal letters: '%s'" % illegal)
+
+
+def find_ix(letter):
+    m = [l[1] for l in tiles if l[0] == letter]
+    if len(m) != 1:
+        raise ValueError("Letter '%c' not in the alphabet!" % letter)
+    return m[0]
+
+
+def find_pos(key, letter):
+    p = key.find(letter)
+    if not (0 <= p < size * size):
+        raise ValueError("Letter '%c' not in key?!" % letter)
+    return (p // size, p % size)
+
+
+def add_pos(a, b):
+    return ((a[0] + b[0]) % size, (a[1] + b[1]) % size)
+
+
+def sub_pos(a, b):
+    return ((a[0] - b[0]) % size, (a[1] - b[1]) % size)
+
+
+def find_at_pos(key, coord):
+    return key[coord[1] + coord[0] * size]
+
+
+def rotate_right(key, row, n):
+    mid = key[size * row:size * (row + 1)]
+    return key[:size * row] + mid[-n:] + mid[:-n] + key[size * (row + 1):]
+
+
+def rotate_down(key, col, n):
+    lines  = [key[i * size:(i + 1) * size] for i in range(size)]
+    lefts  = [l[:col] for l in lines]
+    mids   = [l[col] for l in lines]
+    rights = [l[col + 1:] for l in lines]
+    mids = mids[-n:] + mids[:-n]
+    return ''.join(lefts[i] + mids[i] + rights[i] for i in range(size))
+
+
+def rotate_marker_right(m, row, n):
+    if m[0] != row:
+        return (m[0], m[1])
+    else:
+        return (m[0], (m[1] + n) % size)
+
+
+def rotate_marker_down(m, col, n):
+    if m[1] != col:
+        return (m[0], m[1])
+    else:
+        return ((m[0] + n) % size, m[1])
+
+
+def derive_key(password):
+    i = 0
+    k = letters
+    for c in password:
+        (row, col) = find_ix(c)
+        k = rotate_down(rotate_right(k, i, col), i, row)
+        i = (i + 1) % size
+    return k
+
+
+def encrypt(plaintext):
+    global key, mp
+
+    ciphertext = ''
+    for p in plaintext:
+        pp = find_pos(key, p)
+        mix = find_ix(find_at_pos(key, mp))
+        cp = add_pos(pp, mix)
+        c = find_at_pos(key, cp)
+        ciphertext += c
+
+        key = rotate_right(key, pp[0], 1)
+        mp = rotate_marker_right(mp, pp[0], 1)
+        cp = find_pos(key, c)
+        key = rotate_down(key, cp[1], 1)
+        mp = rotate_marker_down(mp, cp[1], 1)
+        mp = add_pos(mp, find_ix(c))
+    return ciphertext
+
+
+def decrypt(ciphertext):
+    global key, mp
+ 
+    plaintext = ''
+    for c in ciphertext:
+        cp = find_pos(key, c)
+        mix = find_ix(find_at_pos(key, mp))
+        pp = sub_pos(cp, mix)
+        p = find_at_pos(key, pp)
+        plaintext += p
+
+        key = rotate_right(key, pp[0], 1)
+        mp = rotate_marker_right(mp, pp[0], 1)
+        cp = find_pos(key, c)
+        key = rotate_down(key, cp[1], 1)
+        mp = rotate_marker_down(mp, cp[1], 1)
+        mp = add_pos(mp, find_ix(c))
+    return plaintext
+
+
+def create_random_nonce(size):
+    return ''.join(random.choice(letters) for i in range(size))
+
+
+def encrypt_with_nonce(plaintext):
+    global nonce, nonce_enc
+
+    ciphertext = encrypt(nonce + plaintext)
+    nonce_enc = ciphertext[:nonce_size]
+
+    if nonce_mode==1:
+        return nonce + ciphertext[nonce_size:]
+    else:
+        return ciphertext
+
+
+def decrypt_with_nonce(ciphertext):
+    global nonce, nonce_enc
+
+    if nonce_mode==1:
+        nonce = ciphertext[:nonce_size]
+        nonce_enc = encrypt(nonce)
+        return decrypt(ciphertext[nonce_size:])
+    else:
+        plaintext = decrypt(ciphertext)
+        nonce = plaintext[:nonce_size]
+        nonce_enc = ciphertext[:nonce_size]
+        return plaintext[nonce_size:]
+
+
+def eprint(*args, **kwargs):
+    print(*args, file=sys.stderr, **kwargs)
+
+
+def printinfo(enc=False):
+    eprint('CIPHER    : ' + ("LC4" if size==6 else "LS47"))
+    eprint('ALPHABET  : ' + letters)
+    if args.keywordstring:
+        eprint('KEYWORD   : ' + args.keywordstring)
+    eprint('KEY       : ' + initialkey)  # key variable modified during process?
+    eprint('NONCE     : ' + nonce)
+    eprint('NONCE ENC : ' + nonce_enc)
+    eprint('NONCEMODE : ' + ("Kaminsky" if nonce_mode==1 else "Kratochvil"))
+    if enc:
+        eprint('PLAINTEXT : ' + plaintext)
+        eprint('CIPHERTEXT: ' + ciphertext)
+    else:
+        eprint('CIPHERTEXT: ' + ciphertext)
+        eprint('PLAINTEXT : ' + plaintext)
+
+
+def test1(size):
+    global letters, nonce_mode, tiles, noncelen, nonce, nonce_size, nonce_enc, signature
+    global ciphertext, plaintext, key, initialkey, mp
+
+    if size == 7:
+        CIPHERNAME = "LS47"
+        letters = letters7;
+        nonce_mode = 2
+        noncelen=10; nonce = create_random_nonce(noncelen)
+        # nonce = 'dr0+:_pij2'  # just a sample for testing fixed nonce
+    else:
+        CIPHERNAME = "LC4"
+        letters = letters6;
+        nonce_mode = 1
+        noncelen=6; nonce = create_random_nonce(noncelen)
+        # nonce = 'pjpm5i'  # just a sample for testing fixed nonce
+
+    tiles = list(zip(letters, [(x // size, x % size) for x in range(size * size)]))
+    check_nonce(nonce)
+    nonce_size = len(nonce)
+    nonce_enc = ""
+
+    print('\n' + CIPHERNAME)
+
+    if size == 7:
+        keyword = 's3cret_p4ssw0rd/31337'; args.keywordstring=keyword
+        key = derive_key(keyword)
+    else:
+        key = letters
+    initialkey = key
+    check_key(key)
+    mp = (0, 0)
+
+    if size == 7:
+        plaintext = 'conflagrate_the_rose_bush_at_six!'
+        signature = 'peace-vector-3'
+    else:
+        plaintext = 'its_my_fathers_son_but_not_my_brother'
+        signature = '#its_me'   # signature = ''
+
+    check_plaintext(plaintext)
+    ciphertext = encrypt_with_nonce(plaintext)
+
+    key = initialkey; mp = (0, 0)  # initialization again
+    check_ciphertext(ciphertext)
+    decryptedtext = decrypt_with_nonce(ciphertext)
+    print('decrypted text: ' + decryptedtext)
+
+    printinfo(True)
+    args.keywordstring=''
+
+
+
+if __name__ == '__main__':
+
+    parser = argparse.ArgumentParser()
+
+    mgroup = parser.add_mutually_exclusive_group()
+    parser.add_argument("-v", "--verbose", help="output additional information on stderr", action="count", default=0)
+    mgroup.add_argument("-6", "--lc4", help="use ElsieFour cipher (6x6 table) (default)", action="store_true")
+    mgroup.add_argument("-7", "--ls47", help="use LS47 cipher (7x7 table)", action="store_true")
+    mgroup2 = parser.add_mutually_exclusive_group()
+    mgroup2.add_argument("-ks", "--keystring", metavar="STRING", help="use STRING as key")
+    mgroup2.add_argument("-kf", "--keyfile", metavar="FILE", help="read key from FILE")
+    mgroup2.add_argument("-ws", "--keywordstring", metavar="STRING", help="generate key from keyword STRING", default=None)
+    mgroup2.add_argument("-wf", "--keywordfile", metavar="FILE", help="read keyword from FILE to generate key", default=None)
+    mgroup3 = parser.add_mutually_exclusive_group()
+    mgroup3.add_argument("-nl", "--noncelen", metavar="LENGTH", help="use random nonce of length LENGTH", type=int, default=0)
+    mgroup3.add_argument("-ns", "--noncestring", metavar="STRING", help="use STRING as nonce")
+    parser.add_argument("-n0", "--nKaminsky", help="use nonce in Kaminsky mode (default for LC4)", action="store_true")
+    parser.add_argument("-n1", "--nKratochvil", help="use nonce in Kratochvil mode (default for LS47)", action="store_true")
+    mgroup4 = parser.add_mutually_exclusive_group()
+    mgroup4.add_argument("-es", "--encryptstring", metavar="STRING", help="encrypt STRING")
+    mgroup4.add_argument("-ef", "--encryptfile", metavar="FILE", help="read plaintext from FILE and encrypt it")
+    mgroup4.add_argument("-ds", "--decryptstring", metavar="STRING", help="decrypt STRING")
+    mgroup4.add_argument("-df", "--decryptfile", metavar="FILE", help="read ciphertext from FILE and decrypt it")
+    mgroup4.add_argument("-t", "--test", help="encrypt and decrypt a string with a random nonce and a given key (once with LC4 and once with LS47)", action="store_true")
+    parser.add_argument("-s", "--signature", help="append SIGNATURE to plaintext when encrypting")
+
+    args = parser.parse_args()
+
+    if len(sys.argv)==1:
+        parser.print_help()
+        sys.exit(1)
+    if args.verbose and len(sys.argv)==2:
+        print('Version: ' + version)
+        # parser.print_help()
+        sys.exit(1)
+
+    # set cipher
+
+    if args.ls47:
+        size = 7
+        letters = letters7
+    else:
+        size = 6
+        letters = letters6
+
+    tiles = list(zip(letters, [(x // size, x % size) for x in range(size * size)]))
+
+    # set nonce
+
+    if args.noncestring:
+        nonce = args.noncestring
+    elif args.noncelen:
+        nonce = create_random_nonce(args.noncelen)
+    else:
+        nonce = ""
+
+    check_nonce(nonce)
+    nonce_size = len(nonce)
+    nonce_enc = ""
+
+    # set nonce mode
+
+    nonce_mode = 1 if size==6 else 2
+    if args.nKaminsky: nonce_mode = 1
+    if args.nKratochvil: nonce_mode = 2
+
+    # set key
+
+    key = letters
+
+    if args.keywordfile: args.keywordstring = open(args.keywordfile, 'r').read().rstrip('\r\n')
+    if args.keywordstring: key = derive_key(args.keywordstring);
+
+    if args.keyfile: args.keystring = open(args.keyfile, 'r').read().rstrip('\r\n')
+    if args.keystring: key = args.keystring;
+
+    initialkey = key
+    check_key(key)
+
+    mp = (0, 0)
+
+    # encrypt / decrypt / test
+
+    if args.encryptfile:
+        args.encryptstring = open(args.encryptfile, 'r').read().rstrip('\r\n')
+
+    if args.decryptfile:
+        args.decryptstring = open(args.decryptfile, 'r').read().rstrip('\r\n')
+
+    if args.encryptstring:
+        plaintext = args.encryptstring
+        if args.signature: plaintext += args.signature
+        check_plaintext(plaintext)
+        ciphertext = encrypt_with_nonce(plaintext)
+        if args.verbose: printinfo(True)
+        print(ciphertext)
+
+    elif args.decryptstring:
+        ciphertext = args.decryptstring
+        check_ciphertext(ciphertext)
+        plaintext = decrypt_with_nonce(ciphertext)
+        if args.verbose: printinfo()
+        if args.signature and args.verbose:
+            eprint("Warning: the given signature is ignored during decryption")
+        print(plaintext)
+
+    elif args.test:
+        print('\nVersion: ' + version)
+        print('Test: No nonce provided (only its length), so each call will produce a different ciphertext.')
+        size = 7; test1(size)
+        size = 6; test1(size)
+        sys.exit(1)
+
+    else:
+        # if args.verbose: print('Version   : ' + version)
+        print('ALPHABET  : ' + letters)
+        print('KEY       : ' + initialkey)
+        print('NONCE     : ' + nonce)