def _entropy_checksum(entropy: Entropy) -> Tuple[BinStr, BinStr]:
"""Return the checksum of the binary string input entropy.
Entropy must be expressed as binary 0/1 string and
must be 128, 160, 192, 224, or 256 bits.
Leading zeros are considered genuine entropy, not redundant padding.
"""
bin_str_entropy = bin_str_entropy_from_entropy(entropy)
bytes_entropy = bytes_entropy_from_str(bin_str_entropy)
# 256-bit checksum
bytes_checksum = sha256(bytes_entropy).digest()
# integer checksum (leading zeros are lost)
int_checksum = int.from_bytes(bytes_checksum,
byteorder="big",
signed=False)
# convert checksum to binary '01' string
checksum = bin(int_checksum)[2:] # remove '0b'
checksum = checksum.zfill(256) # pad with leading lost zeros
# leftmost bits
checksum_bits = len(bytes_entropy) // 4
return bin_str_entropy, checksum[:checksum_bits]
def test_exceptions() -> None:
bin_str_entropy216 = "00011010" * 27 # 216 bits
bin_str_entropy214 = bin_str_entropy216[:-2] # 214 bits
entropy = bin_str_entropy_from_entropy(bin_str_entropy214, 214)
assert entropy == bin_str_entropy214
# 214 is not in [128, 160, 192, 224, 256, 512]
err_msg = "invalid number of bits: "
with pytest.raises(BTClibValueError, match=err_msg):
bin_str_entropy_from_entropy(bin_str_entropy214)
# 214 is not in [216]
err_msg = "invalid number of bits: "
with pytest.raises(BTClibValueError, match=err_msg):
bin_str_entropy_from_entropy(bin_str_entropy214, 216)
int_entropy211 = int(bin_str_entropy214, 2) # 211 bits
assert int_entropy211.bit_length() == 211
entropy = bin_str_entropy_from_entropy(int_entropy211, 214)
assert entropy == bin_str_entropy214
entropy = bin_str_entropy_from_entropy(int_entropy211, 256)
assert len(entropy) == 256
assert int(entropy, 2) == int_entropy211
entropy = bin_str_entropy_from_entropy(int_entropy211)
assert len(entropy) == 224
assert int(entropy, 2) == int_entropy211
err_msg = "Negative entropy: "
with pytest.raises(BTClibValueError, match=err_msg):
bin_str_entropy_from_entropy(-1 * int_entropy211)
bytes_entropy216 = int_entropy211.to_bytes(27,
byteorder="big",
signed=False)
entropy = bin_str_entropy_from_entropy(bytes_entropy216, 214)
assert entropy == bin_str_entropy214
entropy = bin_str_entropy_from_entropy(bytes_entropy216, 216)
assert entropy != bin_str_entropy216
err_msg = "invalid number of bits: "
with pytest.raises(BTClibValueError, match=err_msg):
bin_str_entropy_from_entropy(bytes_entropy216, 224)
with pytest.raises(BTClibValueError, match=err_msg):
bin_str_entropy_from_entropy(tuple()) # type: ignore
with pytest.raises(ValueError):
bin_str_entropy_from_int("not an int") # type: ignore
with pytest.raises(TypeError):
bin_str_entropy_from_str(3) # type: ignore
err_msg = "invalid number of bits: "
with pytest.raises(BTClibValueError, match=err_msg):
bin_str_entropy = "01" * 65 # 130 bits
bytes_entropy_from_str(bin_str_entropy)