Added new codec: vigenere

Author: dhondta

README.md

@@ -290,6 +290,7 @@ This category also contains `ascii85`, `adobe`, `[x]btoa`, `zeromq` with the `ba
 - [X] `rotN`: aka Caesar cipher (*N* belongs to [1,25])
 - [X] `scytaleN`: encrypts using the number of letters on the rod (*N* belongs to [1,[)
 - [X] `shiftN`: shift ordinals (*N* belongs to [1,255])
+- [X] `vigenere`: aka Vigenere Cipher
 - [X] `xorN`: XOR with a single byte (*N* belongs to [1,255])
 
 > :warning: Crypto functions are of course definitely **NOT** encoding functions ; they are implemented for leveraging the `.encode(...)` API from `codecs`.

docs/pages/enc/crypto.md

@@ -202,6 +202,24 @@ This is a dynamic encoding, that is, it can be called with an integer to define
 
 -----
 
+### Vigenere Cipher
+
+This is a dynamic encoding, that is, it holds the key. There is no default key, meaning that `vigenere` as the encoding scheme throws a `LookupError` indicating that the _key must be a non-empty alphabetic string_.
+
+**Codec** | **Conversions** | **Aliases** | **Comment**
+:---: | :---: | --- | ---
+`vigenere` | text <-> Vigenere ciphertext | `vigenere-abcdef`, `vigenere_MySuperSecret` | key only consists of characters, not digits
+
+```python
+>>> codext.encode("This is a test !", "vigenere-abababa")
+'Tiit it a tfsu !'
+>>> codext.encode("This is a test !", "vigenere_MySuperSecret")
+'Ffam xw r liuk !'
+>>> codext.decode("Tiit it a tfsu !", "vigenere-abababa")
+```
+
+-----
+
 ### XOR with 1 byte
 
 This is a dynamic encoding, that is, it can be called with an integer to define the ordinal of the byte to XOR with the input text.

src/codext/crypto/__init__.py

@@ -9,5 +9,6 @@
 from .rot import *
 from .scytale import *
 from .shift import *
+from .vigenere import *
 from .xor import *
 

src/codext/crypto/vigenere.py

@@ -0,0 +1,65 @@
+# -*- coding: UTF-8 -*-
+"""Vigenere Cipher Codec - vigenere content encoding.
+
+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)
+"""
+from string import ascii_lowercase as LC, ascii_uppercase as UC
+
+from ..__common__ import *
+
+
+__examples__ = {
+    'enc(vigenere)':             None,
+    'enc(vigenere-lemon)':       {'ATTACKATDAWN': 'LXFOPVEFRNHR'},
+    'enc(vigenere-key)':         {'hello': 'rijvs'},
+    'enc(vigenère_key)':         {'Hello World': 'Rijvs Uyvjn'},
+    'enc-dec(vigenere-secret)':  ['hello world', 'ATTACK AT DAWN', 'Test 1234!'],
+}
+__guess__ = ["vigenere-key", "vigenere-secret", "vigenere-password"]
+
+
+__char = lambda c, k, i, d=False: (LC if (b := c in LC) else UC)[(ord(c) - ord("Aa"[b]) + \
+                                                                  [1, -1][d] * (ord(k[i % len(k)]) - ord('a'))) % 26]
+
+
+def __check(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")
+    return key
+
+
+def vigenere_encode(key):
+    def encode(text, errors="strict"):
+        result, i, k = [], 0, __check(key)
+        for c in ensure_str(text):
+            if c in LC or c in UC:
+                result.append(__char(c, k, i))
+                i += 1
+            else:
+                result.append(c)
+        r = "".join(result)
+        return r, len(r)
+    return encode
+
+
+def vigenere_decode(key):
+    def decode(text, errors="strict"):
+        result, i, k = [], 0, __check(key)
+        for c in ensure_str(text):
+            if c in LC or c in UC:
+                result.append(__char(c, k, i, True))
+                i += 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=.1)
+