+BN_div() divides I<a> by I<d> and places the result in I<dv> and the
+remainder in I<rem> (C<dv=a/d, rem=a%d>). Either of I<dv> and I<rem> may
+be B<NULL>, in which case the respective value is not returned.
+The result is rounded towards zero; thus if I<a> is negative, the
+remainder will be zero or negative.
+For division by powers of 2, use BN_rshift(3).
+
+BN_mod() corresponds to BN_div() with I<dv> set to B<NULL>.
+
+BN_nnmod() reduces I<a> modulo I<m> and places the non-negative
+remainder in I<r>.
+
+BN_mod_add() adds I<a> to I<b> modulo I<m> and places the non-negative
+result in I<r>.
+
+BN_mod_sub() subtracts I<b> from I<a> modulo I<m> and places the
+non-negative result in I<r>.
+
+BN_mod_mul() multiplies I<a> by I<b> and finds the non-negative
+remainder respective to modulus I<m> (C<r=(a*b) mod m>). I<r> may be
+the same B<BIGNUM> as I<a> or I<b>. For more efficient algorithms for
+repeated computations using the same modulus, see
+L<BN_mod_mul_montgomery(3)|BN_mod_mul_montgomery(3)> and
+L<BN_mod_mul_reciprocal(3)|BN_mod_mul_reciprocal(3)>.