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136 .\"
137 .IX Title "BN_add 3"
138 .TH BN_add 3 "2009-07-19" "1.0.1n" "OpenSSL"
139 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
140 .\" way too many mistakes in technical documents.
141 .if n .ad l
142 .nh
143 .SH "NAME"
144 BN_add, BN_sub, BN_mul, BN_sqr, BN_div, BN_mod, BN_nnmod, BN_mod_add,
145 BN_mod_sub, BN_mod_mul, BN_mod_sqr, BN_exp, BN_mod_exp, BN_gcd \-
146 arithmetic operations on BIGNUMs
147 .SH "LIBRARY"
148 libcrypto, -lcrypto
149 .SH "SYNOPSIS"
150 .IX Header "SYNOPSIS"
151 .Vb 1
152 \& #include <openssl/bn.h>
153 \&
154 \& int BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b);
155 \&
156 \& int BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b);
157 \&
158 \& int BN_mul(BIGNUM *r, BIGNUM *a, BIGNUM *b, BN_CTX *ctx);
159 \&
160 \& int BN_sqr(BIGNUM *r, BIGNUM *a, BN_CTX *ctx);
161 \&
162 \& int BN_div(BIGNUM *dv, BIGNUM *rem, const BIGNUM *a, const BIGNUM *d,
163 \& BN_CTX *ctx);
164 \&
165 \& int BN_mod(BIGNUM *rem, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx);
166 \&
167 \& int BN_nnmod(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx);
168 \&
169 \& int BN_mod_add(BIGNUM *r, BIGNUM *a, BIGNUM *b, const BIGNUM *m,
170 \& BN_CTX *ctx);
171 \&
172 \& int BN_mod_sub(BIGNUM *r, BIGNUM *a, BIGNUM *b, const BIGNUM *m,
173 \& BN_CTX *ctx);
174 \&
175 \& int BN_mod_mul(BIGNUM *r, BIGNUM *a, BIGNUM *b, const BIGNUM *m,
176 \& BN_CTX *ctx);
177 \&
178 \& int BN_mod_sqr(BIGNUM *r, BIGNUM *a, const BIGNUM *m, BN_CTX *ctx);
179 \&
180 \& int BN_exp(BIGNUM *r, BIGNUM *a, BIGNUM *p, BN_CTX *ctx);
181 \&
182 \& int BN_mod_exp(BIGNUM *r, BIGNUM *a, const BIGNUM *p,
183 \& const BIGNUM *m, BN_CTX *ctx);
184 \&
185 \& int BN_gcd(BIGNUM *r, BIGNUM *a, BIGNUM *b, BN_CTX *ctx);
186 .Ve
187 .SH "DESCRIPTION"
188 .IX Header "DESCRIPTION"
189 \&\fIBN_add()\fR adds \fIa\fR and \fIb\fR and places the result in \fIr\fR (\f(CW\*(C`r=a+b\*(C'\fR).
190 \&\fIr\fR may be the same \fB\s-1BIGNUM\s0\fR as \fIa\fR or \fIb\fR.
191 .PP
192 \&\fIBN_sub()\fR subtracts \fIb\fR from \fIa\fR and places the result in \fIr\fR (\f(CW\*(C`r=a\-b\*(C'\fR).
193 .PP
194 \&\fIBN_mul()\fR multiplies \fIa\fR and \fIb\fR and places the result in \fIr\fR (\f(CW\*(C`r=a*b\*(C'\fR).
195 \&\fIr\fR may be the same \fB\s-1BIGNUM\s0\fR as \fIa\fR or \fIb\fR.
196 For multiplication by powers of 2, use \fIBN_lshift\fR\|(3).
197 .PP
198 \&\fIBN_sqr()\fR takes the square of \fIa\fR and places the result in \fIr\fR
199 (\f(CW\*(C`r=a^2\*(C'\fR). \fIr\fR and \fIa\fR may be the same \fB\s-1BIGNUM\s0\fR.
200 This function is faster than BN_mul(r,a,a).
201 .PP
202 \&\fIBN_div()\fR divides \fIa\fR by \fId\fR and places the result in \fIdv\fR and the
203 remainder in \fIrem\fR (\f(CW\*(C`dv=a/d, rem=a%d\*(C'\fR). Either of \fIdv\fR and \fIrem\fR may
204 be \fB\s-1NULL\s0\fR, in which case the respective value is not returned.
205 The result is rounded towards zero; thus if \fIa\fR is negative, the
206 remainder will be zero or negative.
207 For division by powers of 2, use \fIBN_rshift\fR\|(3).
208 .PP
209 \&\fIBN_mod()\fR corresponds to \fIBN_div()\fR with \fIdv\fR set to \fB\s-1NULL\s0\fR.
210 .PP
211 \&\fIBN_nnmod()\fR reduces \fIa\fR modulo \fIm\fR and places the non-negative
212 remainder in \fIr\fR.
213 .PP
214 \&\fIBN_mod_add()\fR adds \fIa\fR to \fIb\fR modulo \fIm\fR and places the non-negative
215 result in \fIr\fR.
216 .PP
217 \&\fIBN_mod_sub()\fR subtracts \fIb\fR from \fIa\fR modulo \fIm\fR and places the
218 non-negative result in \fIr\fR.
219 .PP
220 \&\fIBN_mod_mul()\fR multiplies \fIa\fR by \fIb\fR and finds the non-negative
221 remainder respective to modulus \fIm\fR (\f(CW\*(C`r=(a*b) mod m\*(C'\fR). \fIr\fR may be
222 the same \fB\s-1BIGNUM\s0\fR as \fIa\fR or \fIb\fR. For more efficient algorithms for
223 repeated computations using the same modulus, see
224 \&\fIBN_mod_mul_montgomery\fR\|(3) and
225 \&\fIBN_mod_mul_reciprocal\fR\|(3).
226 .PP
227 \&\fIBN_mod_sqr()\fR takes the square of \fIa\fR modulo \fBm\fR and places the
228 result in \fIr\fR.
229 .PP
230 \&\fIBN_exp()\fR raises \fIa\fR to the \fIp\fR\-th power and places the result in \fIr\fR
231 (\f(CW\*(C`r=a^p\*(C'\fR). This function is faster than repeated applications of
232 \&\fIBN_mul()\fR.
233 .PP
234 \&\fIBN_mod_exp()\fR computes \fIa\fR to the \fIp\fR\-th power modulo \fIm\fR (\f(CW\*(C`r=a^p %
235 m\*(C'\fR). This function uses less time and space than \fIBN_exp()\fR.
236 .PP
237 \&\fIBN_gcd()\fR computes the greatest common divisor of \fIa\fR and \fIb\fR and
238 places the result in \fIr\fR. \fIr\fR may be the same \fB\s-1BIGNUM\s0\fR as \fIa\fR or
239 \&\fIb\fR.
240 .PP
241 For all functions, \fIctx\fR is a previously allocated \fB\s-1BN_CTX\s0\fR used for
242 temporary variables; see \fIBN_CTX_new\fR\|(3).
243 .PP
244 Unless noted otherwise, the result \fB\s-1BIGNUM\s0\fR must be different from
245 the arguments.
246 .SH "RETURN VALUES"
247 .IX Header "RETURN VALUES"
248 For all functions, 1 is returned for success, 0 on error. The return
249 value should always be checked (e.g., \f(CW\*(C`if (!BN_add(r,a,b)) goto err;\*(C'\fR).
250 The error codes can be obtained by \fIERR_get_error\fR\|(3).
251 .SH "SEE ALSO"
252 .IX Header "SEE ALSO"
253 \&\fIopenssl_bn\fR\|(3), \fIERR_get_error\fR\|(3), \fIBN_CTX_new\fR\|(3),
254 \&\fIBN_add_word\fR\|(3), \fIBN_set_bit\fR\|(3)
255 .SH "HISTORY"
256 .IX Header "HISTORY"
257 \&\fIBN_add()\fR, \fIBN_sub()\fR, \fIBN_sqr()\fR, \fIBN_div()\fR, \fIBN_mod()\fR, \fIBN_mod_mul()\fR,
258 \&\fIBN_mod_exp()\fR and \fIBN_gcd()\fR are available in all versions of SSLeay and
259 OpenSSL. The \fIctx\fR argument to \fIBN_mul()\fR was added in SSLeay
260 0.9.1b. \fIBN_exp()\fR appeared in SSLeay 0.9.0.
261 \&\fIBN_nnmod()\fR, \fIBN_mod_add()\fR, \fIBN_mod_sub()\fR, and \fIBN_mod_sqr()\fR were added in
262 OpenSSL 0.9.7.