Add Vigenère cipher codec

src/codext/crypto/__init__.py

@@ -8,5 +8,6 @@
 from .rot import *
 from .scytale import *
 from .shift import *
+from .vigenere import *
 from .xor import *
 

src/codext/crypto/vigenere.py

@@ -0,0 +1,86 @@
+# -*- coding: UTF-8 -*-
+"""Vigenère Cipher Codec - vigenere content encoding.
+
+Method of encrypting alphabetic text by using a series of interwoven Caesar
+ciphers based on the letters of a keyword. Though the 'chiffre indéchiffrable'
+is easy to understand and implement, for three centuries it resisted all
+attempts to break it.
+
+This codec:
+- en/decodes strings from str to str
+- en/decodes strings from bytes to bytes
+- decodes file content to str (read)
+- encodes file content from str to bytes (write)
+
+Reference: https://en.wikipedia.org/wiki/Vigen%C3%A8re_cipher
+"""
+from string import ascii_lowercase as LC, ascii_uppercase as UC
+
+from ..__common__ import *
+
+
+__examples__ = {
+    'enc(vigenere-lemon)':       {'ATTACKATDAWN': 'LXFOPVEFRNHR'},
+    'enc(vigenere-key)':         {'hello': 'rijvs'},
+    'enc(vigenere_key)':         {'Hello World': 'Rijvs Uyvjn'},
+    'enc-dec(vigenere-secret)':  ['hello world', 'ATTACK AT DAWN', 'Test 1234!'],
+}
+__guess__ = ["vigenere-key", "vigenere-secret", "vigenere-password"]
+
+
+def vigenere_encode(key):
+    key = key.lower()
+    if not key or not key.isalpha():
+        raise LookupError("Bad parameter for encoding 'vigenere': key must be a non-empty alphabetic string")
+
+    def encode(text, errors="strict"):
+        text = ensure_str(text)
+        result = []
+        ki = 0
+        for c in text:
+            if c in LC:
+                shift = ord(key[ki % len(key)]) - ord('a')
+                result.append(LC[(ord(c) - ord('a') + shift) % 26])
+                ki += 1
+            elif c in UC:
+                shift = ord(key[ki % len(key)]) - ord('a')
+                result.append(UC[(ord(c) - ord('A') + shift) % 26])
+                ki += 1
+            else:
+                result.append(c)
+        r = "".join(result)
+        return r, len(r)
+
+    return encode
+
+
+def vigenere_decode(key):
+    key = key.lower()
+    if not key or not key.isalpha():
+        raise LookupError("Bad parameter for encoding 'vigenere': key must be a non-empty alphabetic string")
+
+    def decode(text, errors="strict"):
+        text = ensure_str(text)
+        result = []
+        ki = 0
+        for c in text:
+            if c in LC:
+                shift = ord(key[ki % len(key)]) - ord('a')
+                result.append(LC[(ord(c) - ord('a') - shift) % 26])
+                ki += 1
+            elif c in UC:
+                shift = ord(key[ki % len(key)]) - ord('a')
+                result.append(UC[(ord(c) - ord('A') - shift) % 26])
+                ki += 1
+            else:
+                result.append(c)
+        r = "".join(result)
+        return r, len(r)
+
+    return decode
+
+
+add("vigenere", vigenere_encode, vigenere_decode,
+    r"vigen[eè]re[-_](?:cipher[-_])?([a-zA-Z]+)$",
+    penalty=.2, entropy=lambda e: e, printables_rate=lambda pr: pr,
+    transitive=True, examples=__examples__, guess=__guess__)