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.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\}
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Title "BN_generate_prime 3"
way too many mistakes in technical documents.
Deprecated:
.Vb 2 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
If cb is not \s-1NULL\s0, it is used as follows:
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_ex(). The prime number generation has a negligible error probability.
\fIBN_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 \fBp is composite; if p passes all these tests, it is considered prime.
\fIBN_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 \s-1NULL\s0, \fBBN_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 \fBnchecks == 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 \s-1NULL\s0, BN_GENCB_call(cb, 1, j) 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.
BN_GENCB_call calls the callback function held in the \s-1BN_GENCB\s0 structure and passes the ints a and b as arguments. There are two types of \fB\s-1BN_GENCB\s0 structure that are supported: \*(L"new\*(R" style and \*(L"old\*(R" style. New programs should prefer the \*(L"new\*(R" style, whilst the \*(L"old\*(R" style is provided for backwards compatibility purposes.
For \*(L"new\*(R" style callbacks a \s-1BN_GENCB\s0 structure should be initialised with a call to BN_GENCB_set, where gencb is a \s-1BN_GENCB\s0 *, callback is of type int (*callback)(int, int, \s-1BN_GENCB\s0 *) and cb_arg is a void *. \*(L"Old\*(R" style callbacks are the same except they are initialised with a call to BN_GENCB_set_old and callback is of type \fBvoid (*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.
\fIBN_is_prime_ex(), BN_is_prime_fasttest_ex(), BN_is_prime() and \fIBN_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.
\fIBN_generate_prime() returns the prime number on success, \s-1NULL\s0 otherwise.
Callback functions should return 1 on success or 0 on error.
The error codes can be obtained by ERR_get_error\|(3).