Merge pull request #77 from jinnerbichler/seed_check

Issue #45: Seed check

Author: todofixthis

.gitignore

@@ -21,4 +21,4 @@ docs/_build/
 # Note:  For environment- or IDE-specific metadata (e.g., .DS_Store, .idea, etc.
 # you can add these to your own "global" .gitignore file.
 # https://help.github.com/articles/ignoring-files/#create-a-global-gitignore
-#
+#

iota/crypto/__init__.py

@@ -20,3 +20,10 @@
 Fragments are used to divide up really long tryte sequences into
 manageable chunks (similar in concept to AES blocks).
 """
+
+
+class SeedWarning(Warning):
+  """
+  Warning for inappropriate seeds.
+  """
+  pass

iota/crypto/types.py

@@ -2,9 +2,10 @@
 from __future__ import absolute_import, division, print_function, \
   unicode_literals
 
+import warnings
 from typing import MutableSequence, Optional, Tuple
 
-from iota.crypto import FRAGMENT_LENGTH, HASH_LENGTH
+from iota.crypto import FRAGMENT_LENGTH, HASH_LENGTH, SeedWarning
 from iota.crypto.kerl import Kerl
 from iota.exceptions import with_context
 from iota.transaction.base import Bundle
@@ -73,9 +74,22 @@ class Seed(TryteString):
 
   IMPORTANT: For maximum security, a seed must be EXACTLY 81 trytes!
 
+  WARNINGS:
+      .. warning:: :py:class:`SeedWarning` if seed has inappropriate length.
+
   References:
     - https://forum.iota.org/t/why-arent-seeds-longer-than-81-trytes-more-secure/1278
   """
+
+  def __init__(self, trytes=None):
+    # type: (Optional[TrytesCompatible]) -> None
+    if trytes and len(trytes) > Hash.LEN:
+         warnings.warn("Seed has inappropriate length! "
+                       "(https://forum.iota.org/t/why-arent-seeds-longer-than-81-trytes-more-secure/1278)",
+                       category=SeedWarning)
+
+    super(Seed, self).__init__(trytes)
+
   @classmethod
   def random(cls, length=Hash.LEN):
     """

iota/types.py

@@ -31,7 +31,7 @@
 
 
 # Custom types for type hints and docstrings.
-TrytesCompatible  = Union[AnyStr, bytearray, 'TryteString']
+TrytesCompatible = Union[AnyStr, bytearray, 'TryteString']
 
 
 def trits_from_int(n, pad=None):