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Code Issues Releases Wiki Activity

Addressing errata 151300

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This commit is contained in:
Andreas M. Antonopoulos 2015-02-23 17:53:30 -05:00
parent 733bde3e65
commit cd210e356a
2 changed files with 10 additions and 5 deletions
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5
ch04.asciidoc
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@ -553,6 +553,11 @@ include::code/ec-math.py[]
<<ec_math_run>> shows the output produced by running this script.(((range="endofrange", startref="ix_ch04-asciidoc22")))(((range="endofrange", startref="ix_ch04-asciidoc21")))(((range="endofrange", startref="ix_ch04-asciidoc20")))(((range="endofrange", startref="ix_ch04-asciidoc19")))(((range="endofrange", startref="ix_ch04-asciidoc18"))) <<ec_math_run>> shows the output produced by running this script.(((range="endofrange", startref="ix_ch04-asciidoc22")))(((range="endofrange", startref="ix_ch04-asciidoc21")))(((range="endofrange", startref="ix_ch04-asciidoc20")))(((range="endofrange", startref="ix_ch04-asciidoc19")))(((range="endofrange", startref="ix_ch04-asciidoc18")))
[NOTE]
====
The example above uses +os.urandom+ which reflects a cryptographically secure random number generator (CSRNG) provided by the underlying OS. In the case of UNIX-like operating system such as Linux, it draws from +/dev/urandom+ and in the case of Windows calls +CryptGenRandom()+. If a suitable randomness source is not found, +NotImplementedError+ will be raised. While the random number generator used here is for demonstration purposes, it is not appropriate for generating production-quality bitcoin keys as it is not implemented with sufficient security.
====
[[ec_math_run]] [[ec_math_run]]
.Installing the Python ECDSA library and running the ec_math.py script .Installing the Python ECDSA library and running the ec_math.py script
==== ====

10
code/ec-math.py
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@ -1,5 +1,5 @@
import ecdsa import ecdsa
import random import os
import time import time
from ecdsa.util import string_to_number, number_to_string from ecdsa.util import string_to_number, number_to_string
@ -20,9 +20,11 @@ curve = curve_secp256k1
generator = generator_secp256k1 generator = generator_secp256k1
def random_secret(): def random_secret():
random_char = lambda: chr(random.randint(0, 255))
convert_to_int = lambda array: int("".join(array).encode("hex"), 16) convert_to_int = lambda array: int("".join(array).encode("hex"), 16)
byte_array = [random_char() for i in range(32)]
# Collect 256 bits of random data from the OS's cryptographically secure random generator
byte_array = os.urandom(32)
return convert_to_int(byte_array) return convert_to_int(byte_array)
def get_point_pubkey(point): def get_point_pubkey(point):
@ -38,8 +40,6 @@ def get_point_pubkey_uncompressed(point):
'%064x' % point.y() '%064x' % point.y()
return key.decode('hex') return key.decode('hex')
# Seed random number generator.
random.seed(time.time())
# Generate a new private key. # Generate a new private key.
secret = random_secret() secret = random_secret()