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Cleaned up/commented BIP 0032 key derivation.

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This commit is contained in:
William Yager 2013-12-18 22:08:52 -06:00
parent 0063edb61b
commit 4e1d6da805
1 changed files with 16 additions and 5 deletions
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21
lib/bitcoin.py
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@ -388,7 +388,6 @@ def bip32_init(seed):
def get_pubkeys_from_secret(secret): def get_pubkeys_from_secret(secret):
# public key # public key
curve = SECP256k1
private_key = ecdsa.SigningKey.from_string( secret, curve = SECP256k1 ) private_key = ecdsa.SigningKey.from_string( secret, curve = SECP256k1 )
public_key = private_key.get_verifying_key() public_key = private_key.get_verifying_key()
K = public_key.to_string() K = public_key.to_string()
@ -397,7 +396,14 @@ def get_pubkeys_from_secret(secret):
# Child private key derivation function (from master private key)
# k = master private key (32 bytes)
# c = master chain code (extra entropy for key derivation) (32 bytes)
# n = the index of the key we want to derive. (only 32 bits will be used)
# If n is negative (i.e. the 32nd bit is set), the resulting private key's
# corresponding public key can NOT be determined without the master private key.
# However, if n is positive, the resulting private key's corresponding
# public key can be determined without the master private key.
def CKD(k, c, n): def CKD(k, c, n):
import hmac import hmac
from ecdsa.util import string_to_number, number_to_string from ecdsa.util import string_to_number, number_to_string
@ -405,17 +411,22 @@ def CKD(k, c, n):
keypair = EC_KEY(string_to_number(k)) keypair = EC_KEY(string_to_number(k))
K = GetPubKey(keypair.pubkey,True) K = GetPubKey(keypair.pubkey,True)
if n & BIP32_PRIME: if n & BIP32_PRIME: # We want to make a "secret" address that can't be determined from K
data = chr(0) + k + rev_hex(int_to_hex(n,4)).decode('hex') data = chr(0) + k + rev_hex(int_to_hex(n,4)).decode('hex')
I = hmac.new(c, data, hashlib.sha512).digest() I = hmac.new(c, data, hashlib.sha512).digest()
else: else: # We want a "non-secret" address that can be determined from K
I = hmac.new(c, K + rev_hex(int_to_hex(n,4)).decode('hex'), hashlib.sha512).digest() I = hmac.new(c, K + rev_hex(int_to_hex(n,4)).decode('hex'), hashlib.sha512).digest()
k_n = number_to_string( (string_to_number(I[0:32]) + string_to_number(k)) % order , order ) k_n = number_to_string( (string_to_number(I[0:32]) + string_to_number(k)) % order , order )
c_n = I[32:] c_n = I[32:]
return k_n, c_n return k_n, c_n
# Child public key derivation function (from public key only)
# K = master public key
# c = master chain code
# n = index of key we want to derive
# This function allows us to find the nth public key, as long as n is
# non-negative. If n is negative, we need the master private key to find it.
def CKD_prime(K, c, n): def CKD_prime(K, c, n):
import hmac import hmac
from ecdsa.util import string_to_number, number_to_string from ecdsa.util import string_to_number, number_to_string