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Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH "NAME" BN_rand, BN_pseudo_rand, BN_rand_range, BN_pseudo_rand_range \- generate pseudo\-random number .SH "SYNOPSIS" .IX Header "SYNOPSIS" .Vb 1 \& #include \& \& int BN_rand(BIGNUM *rnd, int bits, int top, int bottom); \& \& int BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom); \& \& int BN_rand_range(BIGNUM *rnd, BIGNUM *range); \& \& int BN_pseudo_rand_range(BIGNUM *rnd, BIGNUM *range); .Ve .SH "DESCRIPTION" .IX Header "DESCRIPTION" \&\fIBN_rand()\fR generates a cryptographically strong pseudo-random number of \&\fBbits\fR in length and stores it in \fBrnd\fR. If \fBbits\fR is less than zero, or too small to accommodate the requirements specified by the \fBtop\fR and \fBbottom\fR parameters, an error is returned. The \fBtop\fR parameters specifies requirements on the most significant bit of the generated number. If it is \fB\s-1BN_RAND_TOP_ANY\s0\fR, there is no constraint. If it is \fB\s-1BN_RAND_TOP_ONE\s0\fR, the top bit must be one. If it is \fB\s-1BN_RAND_TOP_TWO\s0\fR, the two most significant bits of the number will be set to 1, so that the product of two such random numbers will always have 2*\fBbits\fR length. If \fBbottom\fR is \fB\s-1BN_RAND_BOTTOM_ODD\s0\fR, the number will be odd; if it is \fB\s-1BN_RAND_BOTTOM_ANY\s0\fR it can be odd or even. If \fBbits\fR is 1 then \fBtop\fR cannot also be \fB\s-1BN_RAND_FLG_TOPTWO\s0\fR. .PP \&\fIBN_pseudo_rand()\fR does the same, but pseudo-random numbers generated by this function are not necessarily unpredictable. They can be used for non-cryptographic purposes and for certain purposes in cryptographic protocols, but usually not for key generation etc. .PP \&\fIBN_rand_range()\fR generates a cryptographically strong pseudo-random number \fBrnd\fR in the range 0 <= \fBrnd\fR < \fBrange\fR. \&\fIBN_pseudo_rand_range()\fR does the same, but is based on \fIBN_pseudo_rand()\fR, and hence numbers generated by it are not necessarily unpredictable. .PP The \s-1PRNG\s0 must be seeded prior to calling \fIBN_rand()\fR or \fIBN_rand_range()\fR. .SH "RETURN VALUES" .IX Header "RETURN VALUES" The functions return 1 on success, 0 on error. The error codes can be obtained by \fIERR_get_error\fR\|(3). .SH "SEE ALSO" .IX Header "SEE ALSO" \&\fIERR_get_error\fR\|(3), \fIRAND_add\fR\|(3), \fIRAND_bytes\fR\|(3) .SH "COPYRIGHT" .IX Header "COPYRIGHT" Copyright 2000\-2017 The OpenSSL Project Authors. All Rights Reserved. .PP Licensed under the OpenSSL license (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at .