"f1ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff7f",
			"0400000000000000000000000000000000000000000000000000000000000000",
		},
		{
			"y=p+4,sign-",
			"f1ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff",
			"0400000000000000000000000000000000000000000000000000000000000080",
		},
		{
			"y=p+5,sign+",
			"f2ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff7f",

IHDR {
    width: 32; height: 32; bitdepth: 8;
    using grayscale;
}
gAMA {1.0000}
bKGD {gray: 0;}
tRNS {
    gray: 255;
}
IMAGE {
    pixels hex
ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
ffffffffffffffffffffffffffffddcceeffffffffffffffffffffffffffffff
ffffffffffffffffffffffeebb776655446699ddffffffffffffffffffffffff

	want = "693e47972caf527c7883ad1b39822f026f47db2ab0e1919955b8993aa04411d1"
	if got := hex.EncodeToString(p.Bytes()); got != want {
		t.Errorf("zero: got %q, want %q", got, want)
	}

	one := "ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"
	s, _ = new(Scalar).SetBytesWithClamping(decodeHex(one))
	p = new(Point).ScalarBaseMult(s)
	want = "12e9a68b73fd5aacdbcaf3e88c46fea6ebedb1aa84eed1842f07f8edab65e3a7"

		// Order of the curve and above.
		"ffffffff00000000ffffffffffffffffbce6faada7179e84f3b9cac2fc632551",
		"ffffffff00000000ffffffffffffffffbce6faada7179e84f3b9cac2fc632552",
		"ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff",
	},
	ecdh.P384(): {
		// Bad lengths.
		"",
		"01",
		"0101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101",

		{
			"0100000000000000000000000000000000000000000000000000000000000000",
			"0400000000000000000000000000000000000000000000000000000000000000",
			1, "f6ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff3f",
		},
	}

	for i, tt := range tests {
		u, _ := new(Element).SetBytes(decodeHex(tt.u))
		v, _ := new(Element).SetBytes(decodeHex(tt.v))