1 .\" Automatically generated by Pod::Man version 1.15
2 .\" Wed Feb 19 16:42:47 2003
5 .\" ======================================================================
6 .de Sh \" Subsection heading
14 .de Sp \" Vertical space (when we can't use .PP)
20 .ie \\n(.$>=3 .ne \\$3
24 .de Vb \" Begin verbatim text
29 .de Ve \" End verbatim text
34 .\" Set up some character translations and predefined strings. \*(-- will
35 .\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left
36 .\" double quote, and \*(R" will give a right double quote. | will give a
37 .\" real vertical bar. \*(C+ will give a nicer C++. Capital omega is used
38 .\" to do unbreakable dashes and therefore won't be available. \*(C` and
39 .\" \*(C' expand to `' in nroff, nothing in troff, for use with C<>
41 .ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p'
45 . if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch
46 . if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch
59 .\" If the F register is turned on, we'll generate index entries on stderr
60 .\" for titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and
61 .\" index entries marked with X<> in POD. Of course, you'll have to process
62 .\" the output yourself in some meaningful fashion.
65 . tm Index:\\$1\t\\n%\t"\\$2"
71 .\" For nroff, turn off justification. Always turn off hyphenation; it
72 .\" makes way too many mistakes in technical documents.
76 .\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2).
77 .\" Fear. Run. Save yourself. No user-serviceable parts.
79 . \" fudge factors for nroff and troff
88 . ds #H ((1u-(\\\\n(.fu%2u))*.13m)
94 . \" simple accents for nroff and troff
104 . ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u"
105 . ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u'
106 . ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u'
107 . ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u'
108 . ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u'
109 . ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u'
111 . \" troff and (daisy-wheel) nroff accents
112 .ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V'
113 .ds 8 \h'\*(#H'\(*b\h'-\*(#H'
114 .ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#]
115 .ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H'
116 .ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u'
117 .ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#]
118 .ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#]
119 .ds ae a\h'-(\w'a'u*4/10)'e
120 .ds Ae A\h'-(\w'A'u*4/10)'E
121 . \" corrections for vroff
122 .if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u'
123 .if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u'
124 . \" for low resolution devices (crt and lpr)
125 .if \n(.H>23 .if \n(.V>19 \
138 .\" ======================================================================
140 .IX Title "BN_generate_prime 3"
141 .TH BN_generate_prime 3 "0.9.7a" "2003-02-19" "OpenSSL"
144 BN_generate_prime, BN_is_prime, BN_is_prime_fasttest \- generate primes and test for primality
146 .IX Header "SYNOPSIS"
148 \& #include <openssl/bn.h>
151 \& BIGNUM *BN_generate_prime(BIGNUM *ret, int num, int safe, BIGNUM *add,
152 \& BIGNUM *rem, void (*callback)(int, int, void *), void *cb_arg);
155 \& int BN_is_prime(const BIGNUM *a, int checks, void (*callback)(int, int,
156 \& void *), BN_CTX *ctx, void *cb_arg);
159 \& int BN_is_prime_fasttest(const BIGNUM *a, int checks,
160 \& void (*callback)(int, int, void *), BN_CTX *ctx, void *cb_arg,
161 \& int do_trial_division);
164 .IX Header "DESCRIPTION"
165 \&\fIBN_generate_prime()\fR generates a pseudo-random prime number of \fBnum\fR
167 If \fBret\fR is not \fB\s-1NULL\s0\fR, it will be used to store the number.
169 If \fBcallback\fR is not \fB\s-1NULL\s0\fR, it is called as follows:
171 \&\fBcallback(0, i, cb_arg)\fR is called after generating the i-th
172 potential prime number.
174 While the number is being tested for primality, \fBcallback(1, j,
175 cb_arg)\fR is called as described below.
177 When a prime has been found, \fBcallback(2, i, cb_arg)\fR is called.
179 The prime may have to fulfill additional requirements for use in
180 Diffie-Hellman key exchange:
182 If \fBadd\fR is not \fB\s-1NULL\s0\fR, the prime will fulfill the condition p % \fBadd\fR
183 == \fBrem\fR (p % \fBadd\fR == 1 if \fBrem\fR == \fB\s-1NULL\s0\fR) in order to suit a given
186 If \fBsafe\fR is true, it will be a safe prime (i.e. a prime p so
187 that (p-1)/2 is also prime).
189 The \s-1PRNG\s0 must be seeded prior to calling \fIBN_generate_prime()\fR.
190 The prime number generation has a negligible error probability.
192 \&\fIBN_is_prime()\fR and \fIBN_is_prime_fasttest()\fR test if the number \fBa\fR is
193 prime. The following tests are performed until one of them shows that
194 \&\fBa\fR is composite; if \fBa\fR passes all these tests, it is considered
197 \&\fIBN_is_prime_fasttest()\fR, when called with \fBdo_trial_division == 1\fR,
198 first attempts trial division by a number of small primes;
199 if no divisors are found by this test and \fBcallback\fR is not \fB\s-1NULL\s0\fR,
200 \&\fBcallback(1, \-1, cb_arg)\fR is called.
201 If \fBdo_trial_division == 0\fR, this test is skipped.
203 Both \fIBN_is_prime()\fR and \fIBN_is_prime_fasttest()\fR perform a Miller-Rabin
204 probabilistic primality test with \fBchecks\fR iterations. If
205 \&\fBchecks == BN_prime_checks\fR, a number of iterations is used that
206 yields a false positive rate of at most 2^\-80 for random input.
208 If \fBcallback\fR is not \fB\s-1NULL\s0\fR, \fBcallback(1, j, cb_arg)\fR is called
209 after the j-th iteration (j = 0, 1, ...). \fBctx\fR is a
210 pre-allocated \fB\s-1BN_CTX\s0\fR (to save the overhead of allocating and
211 freeing the structure in a loop), or \fB\s-1NULL\s0\fR.
213 .IX Header "RETURN VALUES"
214 \&\fIBN_generate_prime()\fR returns the prime number on success, \fB\s-1NULL\s0\fR otherwise.
216 \&\fIBN_is_prime()\fR returns 0 if the number is composite, 1 if it is
217 prime with an error probability of less than 0.25^\fBchecks\fR, and
220 The error codes can be obtained by ERR_get_error(3).
222 .IX Header "SEE ALSO"
223 bn(3), ERR_get_error(3), rand(3)
226 The \fBcb_arg\fR arguments to \fIBN_generate_prime()\fR and to \fIBN_is_prime()\fR
227 were added in SSLeay 0.9.0. The \fBret\fR argument to \fIBN_generate_prime()\fR
228 was added in SSLeay 0.9.1.
229 \&\fIBN_is_prime_fasttest()\fR was added in OpenSSL 0.9.5.