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140 .IX Title "BN_rand 3"
141 .TH BN_rand 3 "0.9.7a" "2003-02-19" "OpenSSL"
144 BN_rand, BN_pseudo_rand \- generate pseudo-random number
146 .IX Header "SYNOPSIS"
148 \& #include <openssl/bn.h>
151 \& int BN_rand(BIGNUM *rnd, int bits, int top, int bottom);
154 \& int BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom);
157 \& int BN_rand_range(BIGNUM *rnd, BIGNUM *range);
160 \& int BN_pseudo_rand_range(BIGNUM *rnd, BIGNUM *range);
163 .IX Header "DESCRIPTION"
164 \&\fIBN_rand()\fR generates a cryptographically strong pseudo-random number of
165 \&\fBbits\fR bits in length and stores it in \fBrnd\fR. If \fBtop\fR is \-1, the
166 most significant bit of the random number can be zero. If \fBtop\fR is 0,
167 it is set to 1, and if \fBtop\fR is 1, the two most significant bits of
168 the number will be set to 1, so that the product of two such random
169 numbers will always have 2*\fBbits\fR length. If \fBbottom\fR is true, the
172 \&\fIBN_pseudo_rand()\fR does the same, but pseudo-random numbers generated by
173 this function are not necessarily unpredictable. They can be used for
174 non-cryptographic purposes and for certain purposes in cryptographic
175 protocols, but usually not for key generation etc.
177 \&\fIBN_rand_range()\fR generates a cryptographically strong pseudo-random
178 number \fBrnd\fR in the range 0 <lt>= \fBrnd\fR < \fBrange\fR.
179 \&\fIBN_pseudo_rand_range()\fR does the same, but is based on \fIBN_pseudo_rand()\fR,
180 and hence numbers generated by it are not necessarily unpredictable.
182 The \s-1PRNG\s0 must be seeded prior to calling \fIBN_rand()\fR or \fIBN_rand_range()\fR.
184 .IX Header "RETURN VALUES"
185 The functions return 1 on success, 0 on error.
186 The error codes can be obtained by ERR_get_error(3).
188 .IX Header "SEE ALSO"
189 bn(3), ERR_get_error(3), rand(3),
190 RAND_add(3), RAND_bytes(3)
193 \&\fIBN_rand()\fR is available in all versions of SSLeay and OpenSSL.
194 \&\fIBN_pseudo_rand()\fR was added in OpenSSL 0.9.5. The \fBtop\fR == \-1 case
195 and the function \fIBN_rand_range()\fR were added in OpenSSL 0.9.6a.
196 \&\fIBN_pseudo_rand_range()\fR was added in OpenSSL 0.9.6c.