def bits_to_target(bits):
"""
Calculate target from bits
:param bits: HEX string, bytes string or integer representation of bits.
:return: integer.
"""
if type(bits) == str:
bits = bytes_from_hex(bits)
if type(bits) == bytes:
return int_from_bytes(bits[1:], 'big') * (2 ** (8 * (bits[0] - 3)))
else:
shift = bits >> 24
target = (bits & 0xffffff) * (1 << (8 * (shift - 3)))
return target
def generate_entropy(strength=256, hex=True):
"""
Generate 128-256 bits entropy bytes string
:param int strength: entropy bits strength, by default is 256 bit.
:param boolean hex: return HEX encoded string result flag, by default True.
:return: HEX encoded or bytes entropy string.
"""
if strength not in [128, 160, 192, 224, 256]:
raise ValueError('strength should be one of the following [128, 160, 192, 224, 256]')
a = random.SystemRandom().randint(0, ECDSA_SEC256K1_ORDER)
i = int((time.time() % 0.01 ) * 100000)
h = a.to_bytes(32, byteorder="big")
# more entropy from system timer and sha256 derivation
while i:
h = hashlib.sha256(h).digest()
i -= 1
if not i and int_from_bytes(h, byteorder="big") > ECDSA_SEC256K1_ORDER:
i += 1
return h[:int(strength/8)] if not hex else h[:int(strength/8)].hex()