Tool for checking TREZOR-generated mnemonic

mnemonic_check.py

@@ -0,0 +1,61 @@
+#!/usr/bin/python
+'''
+    Use this script to cross-check that TREZOR generated valid
+    mnemonic sentence for given internal (TREZOR-generated)
+    and external (computer-generated) entropy.
+'''
+
+import binascii
+import hashlib
+import mnemonic
+
+def generate_entropy(strength, internal_entropy, external_entropy):
+    '''
+    strength - length of produced seed. One of 128, 192, 256
+    random - binary stream of random data from external HRNG
+    '''
+    if strength not in (128, 192, 256):
+        raise Exception("Invalid strength")
+
+    if not internal_entropy:
+        raise Exception("Internal entropy is not provided")
+
+    if len(internal_entropy) < 32:
+        raise Exception("Internal entropy too short")
+
+    if not external_entropy:
+        raise Exception("External entropy is not provided")
+
+    if len(external_entropy) < 32:
+        raise Exception("External entropy too short")
+
+    entropy = hashlib.sha256(internal_entropy + external_entropy).digest()
+    entropy_stripped = entropy[:strength / 8]
+
+    if len(entropy_stripped) * 8 != strength:
+        raise Exception("Entropy length mismatch")
+
+    return entropy_stripped
+
+def main():
+    comp = binascii.unhexlify(raw_input("Please enter computer-generated entropy (in hex): ").strip())
+    trzr = binascii.unhexlify(raw_input("Please enter TREZOR-generated entropy (in hex): ").strip())
+    word_count = int(raw_input("How many words your mnemonic has? "))
+
+    strength = word_count * 32 / 3
+
+    entropy = generate_entropy(strength, trzr, comp)
+
+    words = mnemonic.Mnemonic('english').to_mnemonic(entropy)
+    if not mnemonic.Mnemonic('english').check(words):
+        print "Mnemonic is invalid"
+        return
+
+    if len(words.split(' ')) != word_count:
+        print "Mnemonic length mismatch!"
+        return
+
+    print "Generated mnemonic is:", words
+
+if __name__ == '__main__':
+    main()