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135 .\"
136 .IX Title "BN_add 3"
137 .TH BN_add 3 "2002-09-25" "1.1.0-dev" "OpenSSL"
138 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
139 .\" way too many mistakes in technical documents.
140 .if n .ad l
141 .nh
142 .SH "NAME"
143 BN_add, BN_sub, BN_mul, BN_sqr, BN_div, BN_mod, BN_nnmod, BN_mod_add,
144 BN_mod_sub, BN_mod_mul, BN_mod_sqr, BN_exp, BN_mod_exp, BN_gcd \-
145 arithmetic operations on BIGNUMs
146 .SH "LIBRARY"
147 libcrypto, -lcrypto
148 .SH "SYNOPSIS"
149 .IX Header "SYNOPSIS"
150 .Vb 1
151 \& #include <openssl/bn.h>
152 \&
153 \& int BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b);
154 \&
155 \& int BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b);
156 \&
157 \& int BN_mul(BIGNUM *r, BIGNUM *a, BIGNUM *b, BN_CTX *ctx);
158 \&
159 \& int BN_sqr(BIGNUM *r, BIGNUM *a, BN_CTX *ctx);
160 \&
161 \& int BN_div(BIGNUM *dv, BIGNUM *rem, const BIGNUM *a, const BIGNUM *d,
162 \& BN_CTX *ctx);
163 \&
164 \& int BN_mod(BIGNUM *rem, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx);
165 \&
166 \& int BN_nnmod(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx);
167 \&
168 \& int BN_mod_add(BIGNUM *r, BIGNUM *a, BIGNUM *b, const BIGNUM *m,
169 \& BN_CTX *ctx);
170 \&
171 \& int BN_mod_sub(BIGNUM *r, BIGNUM *a, BIGNUM *b, const BIGNUM *m,
172 \& BN_CTX *ctx);
173 \&
174 \& int BN_mod_mul(BIGNUM *r, BIGNUM *a, BIGNUM *b, const BIGNUM *m,
175 \& BN_CTX *ctx);
176 \&
177 \& int BN_mod_sqr(BIGNUM *r, BIGNUM *a, const BIGNUM *m, BN_CTX *ctx);
178 \&
179 \& int BN_exp(BIGNUM *r, BIGNUM *a, BIGNUM *p, BN_CTX *ctx);
180 \&
181 \& int BN_mod_exp(BIGNUM *r, BIGNUM *a, const BIGNUM *p,
182 \& const BIGNUM *m, BN_CTX *ctx);
183 \&
184 \& int BN_gcd(BIGNUM *r, BIGNUM *a, BIGNUM *b, BN_CTX *ctx);
185 .Ve
186 .SH "DESCRIPTION"
187 .IX Header "DESCRIPTION"
188 \&\fIBN_add()\fR adds \fIa\fR and \fIb\fR and places the result in \fIr\fR (\f(CW\*(C`r=a+b\*(C'\fR).
189 \&\fIr\fR may be the same \fB\s-1BIGNUM\s0\fR as \fIa\fR or \fIb\fR.
190 .PP
191 \&\fIBN_sub()\fR subtracts \fIb\fR from \fIa\fR and places the result in \fIr\fR (\f(CW\*(C`r=a\-b\*(C'\fR).
192 .PP
193 \&\fIBN_mul()\fR multiplies \fIa\fR and \fIb\fR and places the result in \fIr\fR (\f(CW\*(C`r=a*b\*(C'\fR).
194 \&\fIr\fR may be the same \fB\s-1BIGNUM\s0\fR as \fIa\fR or \fIb\fR.
195 For multiplication by powers of 2, use \fIBN_lshift\fR\|(3).
196 .PP
197 \&\fIBN_sqr()\fR takes the square of \fIa\fR and places the result in \fIr\fR
198 (\f(CW\*(C`r=a^2\*(C'\fR). \fIr\fR and \fIa\fR may be the same \fB\s-1BIGNUM\s0\fR.
199 This function is faster than BN_mul(r,a,a).
200 .PP
201 \&\fIBN_div()\fR divides \fIa\fR by \fId\fR and places the result in \fIdv\fR and the
202 remainder in \fIrem\fR (\f(CW\*(C`dv=a/d, rem=a%d\*(C'\fR). Either of \fIdv\fR and \fIrem\fR may
203 be \fB\s-1NULL\s0\fR, in which case the respective value is not returned.
204 The result is rounded towards zero; thus if \fIa\fR is negative, the
205 remainder will be zero or negative.
206 For division by powers of 2, use \fIBN_rshift\fR\|(3).
207 .PP
208 \&\fIBN_mod()\fR corresponds to \fIBN_div()\fR with \fIdv\fR set to \fB\s-1NULL\s0\fR.
209 .PP
210 \&\fIBN_nnmod()\fR reduces \fIa\fR modulo \fIm\fR and places the non-negative
211 remainder in \fIr\fR.
212 .PP
213 \&\fIBN_mod_add()\fR adds \fIa\fR to \fIb\fR modulo \fIm\fR and places the non-negative
214 result in \fIr\fR.
215 .PP
216 \&\fIBN_mod_sub()\fR subtracts \fIb\fR from \fIa\fR modulo \fIm\fR and places the
217 non-negative result in \fIr\fR.
218 .PP
219 \&\fIBN_mod_mul()\fR multiplies \fIa\fR by \fIb\fR and finds the non-negative
220 remainder respective to modulus \fIm\fR (\f(CW\*(C`r=(a*b) mod m\*(C'\fR). \fIr\fR may be
221 the same \fB\s-1BIGNUM\s0\fR as \fIa\fR or \fIb\fR. For more efficient algorithms for
222 repeated computations using the same modulus, see
223 \&\fIBN_mod_mul_montgomery\fR\|(3) and
224 \&\fIBN_mod_mul_reciprocal\fR\|(3).
225 .PP
226 \&\fIBN_mod_sqr()\fR takes the square of \fIa\fR modulo \fBm\fR and places the
227 result in \fIr\fR.
228 .PP
229 \&\fIBN_exp()\fR raises \fIa\fR to the \fIp\fR\-th power and places the result in \fIr\fR
230 (\f(CW\*(C`r=a^p\*(C'\fR). This function is faster than repeated applications of
231 \&\fIBN_mul()\fR.
232 .PP
233 \&\fIBN_mod_exp()\fR computes \fIa\fR to the \fIp\fR\-th power modulo \fIm\fR (\f(CW\*(C`r=a^p %
234 m\*(C'\fR). This function uses less time and space than \fIBN_exp()\fR.
235 .PP
236 \&\fIBN_gcd()\fR computes the greatest common divisor of \fIa\fR and \fIb\fR and
237 places the result in \fIr\fR. \fIr\fR may be the same \fB\s-1BIGNUM\s0\fR as \fIa\fR or
238 \&\fIb\fR.
239 .PP
240 For all functions, \fIctx\fR is a previously allocated \fB\s-1BN_CTX\s0\fR used for
241 temporary variables; see \fIBN_CTX_new\fR\|(3).
242 .PP
243 Unless noted otherwise, the result \fB\s-1BIGNUM\s0\fR must be different from
244 the arguments.
245 .SH "RETURN VALUES"
246 .IX Header "RETURN VALUES"
247 For all functions, 1 is returned for success, 0 on error. The return
248 value should always be checked (e.g., \f(CW\*(C`if (!BN_add(r,a,b)) goto err;\*(C'\fR).
249 The error codes can be obtained by \fIERR_get_error\fR\|(3).
250 .SH "SEE ALSO"
251 .IX Header "SEE ALSO"
252 \&\fIopenssl_bn\fR\|(3), \fIERR_get_error\fR\|(3), \fIBN_CTX_new\fR\|(3),
253 \&\fIBN_add_word\fR\|(3), \fIBN_set_bit\fR\|(3)
254 .SH "HISTORY"
255 .IX Header "HISTORY"
256 \&\fIBN_add()\fR, \fIBN_sub()\fR, \fIBN_sqr()\fR, \fIBN_div()\fR, \fIBN_mod()\fR, \fIBN_mod_mul()\fR,
257 \&\fIBN_mod_exp()\fR and \fIBN_gcd()\fR are available in all versions of SSLeay and
258 OpenSSL. The \fIctx\fR argument to \fIBN_mul()\fR was added in SSLeay
259 0.9.1b. \fIBN_exp()\fR appeared in SSLeay 0.9.0.
260 \&\fIBN_nnmod()\fR, \fIBN_mod_add()\fR, \fIBN_mod_sub()\fR, and \fIBN_mod_sqr()\fR were added in
261 OpenSSL 0.9.7.