python: Add initial prototype

python/passgeny/bhash.py

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+import math
+
+class BhashException(Exception): pass
+
+class Bhash:
+    """
+    Hash manipulation class.
+
+    The hash is internally treated as a big-endinan integer. This allows for
+    easy implementation of operations such as modulo.
+
+    Note: The consumed bits are calculated using math.log() so the exact number
+    may be inprecise.
+    """
+    def __init__(self):
+        self.bhash = None
+        self.bits_avail = 0
+        self.bits_used = 0.0
+
+    def from_bytes(self, buf: bytes):
+        """
+        Initialize a Bhash from a bytes object
+        """
+        self.bhash = int.from_bytes(buf, byteorder='big')
+        self.bits_avail = len(buf) * 8
+        self.bits_used = 0.0
+
+    def modulo(self, mod: int) -> int:
+        """
+        Treat the hash as a bigint and divide it by mod. The hash is updated
+        with the division result while the module value is returned.
+        """
+        self.bits_used += math.log(mod) / math.log(2)
+        if self.bits_used > self.bits_avail:
+            raise BhashException("Consumed all bits in hash")
+
+        r = self.bhash % mod
+        self.bhash //= mod
+
+        return r

python/passgeny/passgeny.py

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+#
+# Requirements: argon2-cffi
+#
+
+import argon2
+import argparse
+import getpass
+import sys
+
+#
+# WARNING: Changing any of the parameters below will affect password generation
+#
+
+# Default SALT to use; this cannot be random since passgeny must
+# generate predictable passwords
+PASSGENY_SALT_DEFAULT = b"Passgeny v1"
+# Memory cost expresssed in kb
+PASSGENY_ARGON2_MEMORY_COST = 8192
+# Number of iterations
+PASSGENY_ARGON2_TIME_COST = 6
+# Number of parallel threads
+PASSGENY_ARGON2_PARALLEL = 4
+# Hash length - 512 bits by default
+PASSGENY_ARGON2_HASH_LEN = 64
+
+def argon2_hash(message):
+    return argon2.low_level.hash_secret_raw(
+            message,
+            PASSGENY_SALT_DEFAULT,
+            type = argon2.Type.ID,
+            memory_cost = PASSGENY_ARGON2_MEMORY_COST,
+            time_cost = PASSGENY_ARGON2_TIME_COST,
+            parallelism = PASSGENY_ARGON2_PARALLEL,
+            hash_len = PASSGENY_ARGON2_HASH_LEN)
+
+def passgeny_hash(master_password, token_list):
+    message = b''
+
+    # Construct the message to be hashed
+    for x in token_list:
+        message += x.encode() + b'\0'
+
+    message += master_password.encode() + b'\0'
+    return argon2_hash(message)
+
+mpw = getpass.getpass("Master password: ")
+print(passgeny_hash(mpw, ("1", "2", "3")))