doc/BN_generate_prime: update doc about other callback values

[openssl.git] / doc / man3 / BN_generate_prime.pod

diff --git a/doc/man3/BN_generate_prime.pod b/doc/man3/BN_generate_prime.pod
index f833d5ced590d39e191208309b35b46812e80e17..08158c193981dadd94b897c9a3fff12b035ef796 100644 (file)
--- a/doc/man3/BN_generate_prime.pod
+++ b/doc/man3/BN_generate_prime.pod
@@ -72,6 +72,11 @@ B<BN_GENCB_call(cb, 1, j)> is called as described below.
 
 When a prime has been found, B<BN_GENCB_call(cb, 2, i)> is called.
 
+=item *
+
+The callers of BN_generate_prime_ex() may call B<BN_GENCB_call(cb, i, j)> with
+other values as described in their respective man pages; see L</SEE ALSO>.
+
 =back
 
 The prime may have to fulfill additional requirements for use in
@@ -101,7 +106,17 @@ If B<do_trial_division == 0>, this test is skipped.
 Both BN_is_prime_ex() and BN_is_prime_fasttest_ex() perform a Miller-Rabin
 probabilistic primality test with B<nchecks> iterations. If
 B<nchecks == BN_prime_checks>, a number of iterations is used that
-yields a false positive rate of at most 2^-80 for random input.
+yields a false positive rate of at most 2^-64 for random input.
+The error rate depends on the size of the prime and goes down for bigger primes.
+The rate is 2^-80 starting at 308 bits, 2^-112 at 852 bits, 2^-128 at 1080 bits,
+2^-192 at 3747 bits and 2^-256 at 6394 bits.
+
+When the source of the prime is not random or not trusted, the number
+of checks needs to be much higher to reach the same level of assurance:
+It should equal half of the targeted security level in bits (rounded up to the
+next integer if necessary).
+For instance, to reach the 128 bit security level, B<nchecks> should be set to
+64.
 
 If B<cb> is not B<NULL>, B<BN_GENCB_call(cb, 1, j)> is called
 after the j-th iteration (j = 0, 1, ...). B<ctx> is a
@@ -177,7 +192,8 @@ Instead applications should create a BN_GENCB structure using BN_GENCB_new:
 
 =head1 SEE ALSO
 
-L<ERR_get_error(3)>, L<RAND_bytes(3)>
+L<DH_generate_parameters(3)>, L<DSA_generate_parameters(3)>,
+L<RSA_generate_key(3)>, L<ERR_get_error(3)>, L<RAND_bytes(3)>
 
 =head1 HISTORY