tmake sure seed last word is uniformly distributed. count prefix length as entropy - electrum - Electrum Bitcoin wallet
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---
DIR commit 569a3b4fab68a61db8c0e6f2362728dd5850c3f5
DIR parent 7982cadd2236a2f998dca91a3bae30ccd6570370
HTML Author: ThomasV <thomasv@electrum.org>
Date: Thu, 22 Sep 2016 14:37:08 +0200
make sure seed last word is uniformly distributed. count prefix length as entropy
Diffstat:
M lib/mnemonic.py | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)
---
DIR diff --git a/lib/mnemonic.py b/lib/mnemonic.py
t@@ -160,13 +160,14 @@ class Mnemonic(object):
return i % custom_entropy == 0
def make_seed(self, num_bits=128, prefix=version.SEED_PREFIX, custom_entropy=1):
- n = int(math.ceil(math.log(custom_entropy,2)))
- # bits of entropy used by the prefix
- k = len(prefix)*4
- # we add at least 16 bits
- n_added = max(16, k + num_bits - n)
- print_error("make_seed", prefix, "adding %d bits"%n_added)
- my_entropy = ecdsa.util.randrange( pow(2, n_added) )
+ # increase num_bits in order to obtain a uniform distibution for the last word
+ bpw = math.log(len(self.wordlist), 2)
+ num_bits = int(math.ceil(num_bits/bpw)) * bpw
+ # handle custom entropy; make sure we add at least 16 bits
+ n_custom = int(math.ceil(math.log(custom_entropy, 2)))
+ n = max(16, num_bits - n_custom)
+ print_error("make_seed", prefix, "adding %d bits"%n)
+ my_entropy = ecdsa.util.randrange(pow(2, n))
nonce = 0
while True:
nonce += 1