Automatically generated by Pod::Man 2.27 (Pod::Simple 3.28)

Standard preamble:
========================================================================
..

..

.. Set up some character translations and predefined strings. \*(-- will
give an unbreakable dash, \*(PI will give pi, \*(L" will give a left
double quote, and \*(R" will give a right double quote. \*(C+ will
give a nicer C++. Capital omega is used to do unbreakable dashes and
therefore won't be available. \*(C` and \*(C' expand to `' in nroff,
nothing in troff, for use with C<>.
.tr \(*W- . ds -- \(*W- . ds PI pi . if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch . if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch . ds L" "" . ds R" "" . ds C` "" . ds C' "" 'br\} . ds -- \|\(em\| . ds PI \(*p . ds L" `` . ds R" '' . ds C` . ds C' 'br\}
Escape single quotes in literal strings from groff's Unicode transform.

If the F register is turned on, we'll generate index entries on stderr for
titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index
entries marked with X<> in POD. Of course, you'll have to process the
output yourself in some meaningful fashion.

Avoid warning from groff about undefined register 'F'.
.. .nr rF 0 . if \nF \{ . de IX . tm Index:\\$1\t\\n%\t"\\$2" .. . if !\nF==2 \{ . nr % 0 . nr F 2 . \} . \} .\} .rr rF
Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2).
Fear. Run. Save yourself. No user-serviceable parts.
. \" fudge factors for nroff and troff . ds #H 0 . ds #V .8m . ds #F .3m . ds #[ \f1 . ds #] .\} . ds #H ((1u-(\\\\n(.fu%2u))*.13m) . ds #V .6m . ds #F 0 . ds #[ \& . ds #] \& .\} . \" simple accents for nroff and troff . ds ' \& . ds ` \& . ds ^ \& . ds , \& . ds ~ ~ . ds / .\} . ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u" . ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u' . ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u' . ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u' . ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u' . ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u' .\} . \" troff and (daisy-wheel) nroff accents . \" corrections for vroff . \" for low resolution devices (crt and lpr) \{\ . ds : e . ds 8 ss . ds o a . ds d- d\h'-1'\(ga . ds D- D\h'-1'\(hy . ds th \o'bp' . ds Th \o'LP' . ds ae ae . ds Ae AE .\} ========================================================================

Title "BN_generate_prime 3" For nroff, turn off justification. Always turn off hyphenation; it makes
way too many mistakes in technical documents.
BN_generate_prime, BN_is_prime, BN_is_prime_fasttest - generate primes and test for primality Header "SYNOPSIS" .Vb 1 #include <openssl/bn.h> \& BIGNUM *BN_generate_prime(BIGNUM *ret, int num, int safe, BIGNUM *add, BIGNUM *rem, void (*callback)(int, int, void *), void *cb_arg); \& int BN_is_prime(const BIGNUM *a, int checks, void (*callback)(int, int, void *), BN_CTX *ctx, void *cb_arg); \& int BN_is_prime_fasttest(const BIGNUM *a, int checks, void (*callback)(int, int, void *), BN_CTX *ctx, void *cb_arg, int do_trial_division); .Ve Header "DESCRIPTION" \fIBN_generate_prime() generates a pseudo-random prime number of num bits. If ret is not \s-1NULL\s0, it will be used to store the number.

If callback is not \s-1NULL\s0, it is called as follows:

\fBcallback(0, i, cb_arg) is called after generating the i-th potential prime number. While the number is being tested for primality, callback(1, j, cb_arg) is called as described below. When a prime has been found, callback(2, i, cb_arg) is called.

The prime may have to fulfill additional requirements for use in Diffie-Hellman key exchange:

If add is not \s-1NULL\s0, the prime will fulfill the condition p % add == rem (p % add == 1 if rem == \s-1NULL\s0) in order to suit a given generator.

If safe is true, it will be a safe prime (i.e. a prime p so that (p-1)/2 is also prime).

The \s-1PRNG\s0 must be seeded prior to calling BN_generate_prime(). The prime number generation has a negligible error probability.

\fIBN_is_prime() and BN_is_prime_fasttest() test if the number a is prime. The following tests are performed until one of them shows that \fBa is composite; if a passes all these tests, it is considered prime.

\fIBN_is_prime_fasttest(), when called with do_trial_division == 1, first attempts trial division by a number of small primes; if no divisors are found by this test and callback is not \s-1NULL\s0, \fBcallback(1, -1, cb_arg) is called. If do_trial_division == 0, this test is skipped.

Both BN_is_prime() and BN_is_prime_fasttest() perform a Miller-Rabin probabilistic primality test with checks iterations. If \fBchecks == BN_prime_checks, a number of iterations is used that yields a false positive rate of at most 2^-80 for random input.

If callback is not \s-1NULL\s0, callback(1, j, cb_arg) is called after the j-th iteration (j = 0, 1, ...). ctx is a pre-allocated \s-1BN_CTX\s0 (to save the overhead of allocating and freeing the structure in a loop), or \s-1NULL\s0.

Header "RETURN VALUES" \fIBN_generate_prime() returns the prime number on success, \s-1NULL\s0 otherwise.

\fIBN_is_prime() returns 0 if the number is composite, 1 if it is prime with an error probability of less than 0.25^checks, and \-1 on error.

The error codes can be obtained by ERR_get_error\|(3).

Header "SEE ALSO" \fIbn\|(3), ERR_get_error\|(3), rand\|(3) Header "HISTORY" The cb_arg arguments to BN_generate_prime() and to BN_is_prime() were added in SSLeay 0.9.0. The ret argument to BN_generate_prime() was added in SSLeay 0.9.1. \fIBN_is_prime_fasttest() was added in OpenSSL 0.9.5.