Background to sec and cnd functions

Starting with GMP 5, we provide a public mpz_powm_sec function, supported by a corresponding mpn_sec_powm and mpn_cnd_sub_n (then called mpn_powm_sec and mpn_subcnd_n, respectively).

Starting with GMP 6, we provide a public set of mpn_sec functions.

The purpose for the sec and cnd functions is providing a basic set of side-channel silent function.

The functions never allocate their own scratch memory, since some applications will surely want to allocate "safe" memory.

Suggested list of functions

function	visibility	status
mpn_sec_powm	public	OK
mpn_sec_mul	public	OK
mpn_sec_sqr	public	OK
mpn_sec_div_qr	public	OK
mpn_sec_div_r	public	OK
mpn_sec_pi1_div_qr	private?	OK
mpn_sec_pi1_div_r	private?	OK
mpn_sec_add_1	public
mpn_sec_sub_1	public
mpn_cnd_neg	public
mpn_cnd_swap	public
mpn_sec_minvert	public	OK
mpn_cnd_add_n	public	OK
mpn_cnd_sub_n	public	OK
mpn_sec_tabselect	public	OK