wip

libs/derive_string.py

@@ -0,0 +1,50 @@
+#!/usr/bin/env python
+
+from hashlib import sha3_256
+from itertools import count
+from Crypto.Cipher import ChaCha20
+from math import floor, ceil
+
+def chacha_bits(input, bit_count):
+    zerobyte = (0).to_bytes(length=1, byteorder='big')
+    cipher = ChaCha20.new(key=sha3_256(input).digest(), nonce=zerobyte*8)
+    i = 0
+
+    while True:
+        start_bit = bit_count * i
+        start_byte = start_bit // 8
+        start_padding = start_bit % 8
+
+        end_bit = bit_count * i + bit_count
+        end_byte = end_bit // 8
+        end_padding = 8 - (end_bit % 8)
+
+        byte_count = end_byte - start_byte
+
+        cipher.seek(start_byte)
+        ciphertext = cipher.encrypt(zerobyte*byte_count)
+        shifted_ciphertext = int.from_bytes(ciphertext, byteorder='big') >> end_padding
+        
+        bit_mask = int('1'*bit_count, 2)
+        masked_ciphertext = shifted_ciphertext & bit_mask
+        
+        yield masked_ciphertext
+        i += 1
+
+
+def chacha_chracter(input, choices):
+    get_bits = chacha_bits(input, len(choices).bit_length())
+    
+    while True:
+        choice = next(get_bits)
+        if choice < len(choices):
+            yield choices[choice]
+
+
+def derive_string(input, length, choices):
+    get_character = chacha_chracter(input, choices)
+    return ''.join(next(get_character) for i in range(length))
+
+print(
+    derive_string(b'12345', length=100, choices='abcde12345')
+)

requirements.txt

@@ -1,2 +1,3 @@
 bundlewrap>=4.8.0
+pycryptodome
 PyNaCl