Function compute_xonly_pubkey

test/functional/test_framework/key.py:406–417

Compute an x-only (32 byte) public key from a (32 byte) private key. This also returns whether the resulting public key was negated.

(key)

        return b'\x30' + bytes([4 + len(rb) + len(sb), 2, len(rb)]) + rb + bytes([2, len(sb)]) + sb

def compute_xonly_pubkey(key):
    """Compute an x-only (32 byte) public key from a (32 byte) private key.

    This also returns whether the resulting public key was negated.
    """

    assert len(key) == 32
    x = int.from_bytes(key, 'big')
    if x == 0 or x >= SECP256K1_ORDER:
        return (None, None)
    P = SECP256K1.affine(SECP256K1.mul([(SECP256K1_G, x)]))
    return (P[0].to_bytes(32, 'big'), not SECP256K1.has_even_y(P))

def tweak_add_privkey(key, tweak):
    """Tweak a private key (after negating it if needed)."""