Add Trithemius cipher codec

src/codext/crypto/__init__.py

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

src/codext/crypto/trithemius.py

@@ -0,0 +1,60 @@
+# -*- coding: UTF-8 -*-
+"""Trithemius Cipher Codec - trithemius content encoding.
+
+The Trithemius cipher is a polyalphabetic encryption method invented by the German
+abbot Johannes Trithemius. It applies a sequence of progressive Caesar shifts (0, 1,
+2, ...) to each successive letter in the plaintext, leaving non-alphabetic characters
+unchanged. It is equivalent to a Vigenère cipher with the key "ABCDEFGHIJKLMNOPQRSTUVWXYZ...".
+
+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://www.dcode.fr/trithemius-cipher
+"""
+from string import ascii_lowercase as LC, ascii_uppercase as UC
+
+from ..__common__ import *
+
+
+__examples__ = {
+    'enc(trithemius|trithemius-cipher)': {'this is a test': "tikv mx g ambd"},
+    'enc(trithemius)': {
+        '':          "",
+        'HELLO':     "HFNOS",
+        '12345!@#$': "12345!@#$",
+    },
+    'enc-dec(trithemius)': ["Hello, World!", "@random"],
+}
+__guess__ = ["trithemius"]
+
+
+def _trithemius(text, decode=False):
+    r, pos = "", 0
+    for c in ensure_str(text):
+        if c in LC:
+            r += LC[(LC.index(c) + (-pos if decode else pos)) % 26]
+            pos += 1
+        elif c in UC:
+            r += UC[(UC.index(c) + (-pos if decode else pos)) % 26]
+            pos += 1
+        else:
+            r += c
+    return r
+
+
+def trithemius_encode(text, errors="strict"):
+    r = _trithemius(ensure_str(text))
+    return r, len(text)
+
+
+def trithemius_decode(text, errors="strict"):
+    r = _trithemius(ensure_str(text), decode=True)
+    return r, len(text)
+
+
+add("trithemius", trithemius_encode, trithemius_decode,
+    r"trithemius(?:[-_]cipher)?$",
+    entropy=lambda e: e, printables_rate=lambda pr: pr, transitive=True)