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131 .IX Title "BN_rand 3"
132 .TH BN_rand 3 "2007-03-15" "0.9.8e" "OpenSSL"
134 BN_rand, BN_pseudo_rand \- generate pseudo\-random number
136 .IX Header "SYNOPSIS"
138 \& #include <openssl/bn.h>
142 \& int BN_rand(BIGNUM *rnd, int bits, int top, int bottom);
146 \& int BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom);
150 \& int BN_rand_range(BIGNUM *rnd, BIGNUM *range);
154 \& int BN_pseudo_rand_range(BIGNUM *rnd, BIGNUM *range);
157 .IX Header "DESCRIPTION"
158 \&\fIBN_rand()\fR generates a cryptographically strong pseudo-random number of
159 \&\fBbits\fR bits in length and stores it in \fBrnd\fR. If \fBtop\fR is \-1, the
160 most significant bit of the random number can be zero. If \fBtop\fR is 0,
161 it is set to 1, and if \fBtop\fR is 1, the two most significant bits of
162 the number will be set to 1, so that the product of two such random
163 numbers will always have 2*\fBbits\fR length. If \fBbottom\fR is true, the
166 \&\fIBN_pseudo_rand()\fR does the same, but pseudo-random numbers generated by
167 this function are not necessarily unpredictable. They can be used for
168 non-cryptographic purposes and for certain purposes in cryptographic
169 protocols, but usually not for key generation etc.
171 \&\fIBN_rand_range()\fR generates a cryptographically strong pseudo-random
172 number \fBrnd\fR in the range 0 <lt>= \fBrnd\fR < \fBrange\fR.
173 \&\fIBN_pseudo_rand_range()\fR does the same, but is based on \fIBN_pseudo_rand()\fR,
174 and hence numbers generated by it are not necessarily unpredictable.
176 The \s-1PRNG\s0 must be seeded prior to calling \fIBN_rand()\fR or \fIBN_rand_range()\fR.
178 .IX Header "RETURN VALUES"
179 The functions return 1 on success, 0 on error.
180 The error codes can be obtained by \fIERR_get_error\fR\|(3).
182 .IX Header "SEE ALSO"
183 \&\fIbn\fR\|(3), \fIERR_get_error\fR\|(3), \fIrand\fR\|(3),
184 \&\fIRAND_add\fR\|(3), \fIRAND_bytes\fR\|(3)
187 \&\fIBN_rand()\fR is available in all versions of SSLeay and OpenSSL.
188 \&\fIBN_pseudo_rand()\fR was added in OpenSSL 0.9.5. The \fBtop\fR == \-1 case
189 and the function \fIBN_rand_range()\fR were added in OpenSSL 0.9.6a.
190 \&\fIBN_pseudo_rand_range()\fR was added in OpenSSL 0.9.6c.