def METHOD_NAME(self):
    # generate an "x" (1 < x < q), where q is (p-1)/2.
    # p is a 128-byte (1024-bit) number, where the first 64 bits are 1.
    # therefore q can be approximated as a 2^1023.  we drop the subset of
    # potential x where the first 63 bits are 1, because some of those
    # will be larger than q (but this is a tiny tiny subset of
    # potential x).
    while 1:
        x_bytes = os.urandom(128)
        x_bytes = byte_mask(x_bytes[0], 0x7F) + x_bytes[1:]
        if (
            x_bytes[:8] != b7fffffffffffffff
            and x_bytes[:8] != b0000000000000000
        ):
            break
    self.x = util.inflate_long(x_bytes)