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BN_is_prime(3)

BN_generate_prime(3)                OpenSSL               BN_generate_prime(3)

NAME
       BN_generate_prime_ex, BN_is_prime_ex, BN_is_prime_fasttest_ex,
       BN_GENCB_call, BN_GENCB_set_old, BN_GENCB_set, BN_generate_prime,
       BN_is_prime, BN_is_prime_fasttest - generate primes and test for
       primality

SYNOPSIS
        #include <openssl/bn.h>

        int BN_generate_prime_ex(BIGNUM *ret,int bits,int safe, const BIGNUM *add,
            const BIGNUM *rem, BN_GENCB *cb);

        int BN_is_prime_ex(const BIGNUM *p,int nchecks, BN_CTX *ctx, BN_GENCB *cb);

        int BN_is_prime_fasttest_ex(const BIGNUM *p,int nchecks, BN_CTX *ctx,
            int do_trial_division, BN_GENCB *cb);

        int BN_GENCB_call(BN_GENCB *cb, int a, int b);

        #define BN_GENCB_set_old(gencb, callback, cb_arg) ...

        #define BN_GENCB_set(gencb, callback, cb_arg) ...

       Deprecated:

        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);

DESCRIPTION
       BN_generate_prime_ex() generates a pseudo-random prime number of bit
       length bits.  If ret is not NULL, it will be used to store the number.

       If cb is not NULL, it is used as follows:

       •   BN_GENCB_call(cb,  0,  i)  is  called  after  generating  the  i-th
           potential prime number.

       •   While the number is being tested for  primality,  BN_GENCB_call(cb,
           1, j) is called as described below.

       •   When a prime has been found, BN_GENCB_call(cb, 2, i) is called.

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

       If add is not NULL, the prime will fulfill the condition p % add == rem
       (p % add == 1 if rem == NULL) 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  PRNG  must be seeded prior to calling BN_generate_prime_ex().  The
       prime number generation has a negligible error probability.

       BN_is_prime_ex() and BN_is_prime_fasttest_ex() test if the number p  is
       prime.   The following tests are performed until one of them shows that
       p is composite; if p passes all these tests, it is considered prime.

       BN_is_prime_fasttest_ex(), 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 cb is not  NULL,  BN_GENCB_call(cb,
       1, -1) is called.  If 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 nchecks iterations. If  nchecks
       ==  BN_prime_checks, a number of iterations is used that yields a false
       positive rate of at most 2^-80 for random input.

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

       BN_GENCB_call  calls  the  callback  function  held  in  the   BN_GENCB
       structure and passes the ints a and b as arguments. There are two types
       of  BN_GENCB structure that are supported: "new" style and "old" style.
       New programs should prefer the "new" style, whilst the "old"  style  is
       provided for backwards compatibility purposes.

       For  "new"  style  callbacks a BN_GENCB structure should be initialised
       with a call to BN_GENCB_set, where gencb is a BN_GENCB *,  callback  is
       of  type  int (*callback)(int, int, BN_GENCB *) and cb_arg is a void *.
       "Old" style callbacks are the same except they are initialised  with  a
       call  to BN_GENCB_set_old and callback is of type void (*callback)(int,
       int, void *).

       A callback is invoked through a call to BN_GENCB_call. This will  check
       the  type of the callback and will invoke callback(a, b, gencb) for new
       style callbacks or callback(a, b, cb_arg) for old style.

       BN_generate_prime   (deprecated)   works   in   the   same    way    as
       BN_generate_prime_ex   but  expects  an  old  style  callback  function
       directly in the callback parameter, and an argument to pass  to  it  in
       the   cb_arg.   Similarly   BN_is_prime  and  BN_is_prime_fasttest  are
       deprecated   and   can    be    compared    to    BN_is_prime_ex    and
       BN_is_prime_fasttest_ex respectively.

RETURN VALUES
       BN_generate_prime_ex() return 1 on success or 0 on error.

       BN_is_prime_ex(),    BN_is_prime_fasttest_ex(),    BN_is_prime()    and
       BN_is_prime_fasttest() return 0 if the number is composite, 1 if it  is
       prime  with  an  error probability of less than 0.25^nchecks, and -1 on
       error.

       BN_generate_prime()  returns  the  prime  number   on   success,   NULL
       otherwise.

       Callback functions should return 1 on success or 0 on error.

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

SEE ALSO
       bn(3), ERR_get_error(3), rand(3)

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.   BN_is_prime_fasttest() was added in OpenSSL
       0.9.5.

1.0.2l                            2017-05-25              BN_generate_prime(3)
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