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.\" ========================================================================
.\"
.IX Title "EVP_RAND-CTR-DRBG 7"
.TH EVP_RAND-CTR-DRBG 7 "2023-05-07" "3.0.9" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
EVP_RAND\-CTR\-DRBG \- The CTR DRBG EVP_RAND implementation
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Support for the counter deterministic random bit generator through the
\&\fB\s-1EVP_RAND\s0\fR \s-1API.\s0
.SS "Identity"
.IX Subsection "Identity"
\&\*(L"CTR-DRBG\*(R" is the name for this implementation; it can be used with the
\&\fBEVP_RAND_fetch()\fR function.
.SS "Supported parameters"
.IX Subsection "Supported parameters"
The supported parameters are:
.ie n .IP """state"" (\fB\s-1OSSL_RAND_PARAM_STATE\s0\fR) <integer>" 4
.el .IP "``state'' (\fB\s-1OSSL_RAND_PARAM_STATE\s0\fR) <integer>" 4
.IX Item "state (OSSL_RAND_PARAM_STATE) <integer>"
.PD 0
.ie n .IP """strength"" (\fB\s-1OSSL_RAND_PARAM_STRENGTH\s0\fR) <unsigned integer>" 4
.el .IP "``strength'' (\fB\s-1OSSL_RAND_PARAM_STRENGTH\s0\fR) <unsigned integer>" 4
.IX Item "strength (OSSL_RAND_PARAM_STRENGTH) <unsigned integer>"
.ie n .IP """max_request"" (\fB\s-1OSSL_RAND_PARAM_MAX_REQUEST\s0\fR) <unsigned integer>" 4
.el .IP "``max_request'' (\fB\s-1OSSL_RAND_PARAM_MAX_REQUEST\s0\fR) <unsigned integer>" 4
.IX Item "max_request (OSSL_RAND_PARAM_MAX_REQUEST) <unsigned integer>"
.ie n .IP """reseed_requests"" (\fB\s-1OSSL_DRBG_PARAM_RESEED_REQUESTS\s0\fR) <unsigned integer>" 4
.el .IP "``reseed_requests'' (\fB\s-1OSSL_DRBG_PARAM_RESEED_REQUESTS\s0\fR) <unsigned integer>" 4
.IX Item "reseed_requests (OSSL_DRBG_PARAM_RESEED_REQUESTS) <unsigned integer>"
.ie n .IP """reseed_time_interval"" (\fB\s-1OSSL_DRBG_PARAM_RESEED_TIME_INTERVAL\s0\fR) <integer>" 4
.el .IP "``reseed_time_interval'' (\fB\s-1OSSL_DRBG_PARAM_RESEED_TIME_INTERVAL\s0\fR) <integer>" 4
.IX Item "reseed_time_interval (OSSL_DRBG_PARAM_RESEED_TIME_INTERVAL) <integer>"
.ie n .IP """min_entropylen"" (\fB\s-1OSSL_DRBG_PARAM_MIN_ENTROPYLEN\s0\fR) <unsigned integer>" 4
.el .IP "``min_entropylen'' (\fB\s-1OSSL_DRBG_PARAM_MIN_ENTROPYLEN\s0\fR) <unsigned integer>" 4
.IX Item "min_entropylen (OSSL_DRBG_PARAM_MIN_ENTROPYLEN) <unsigned integer>"
.ie n .IP """max_entropylen"" (\fB\s-1OSSL_DRBG_PARAM_MAX_ENTROPYLEN\s0\fR) <unsigned integer>" 4
.el .IP "``max_entropylen'' (\fB\s-1OSSL_DRBG_PARAM_MAX_ENTROPYLEN\s0\fR) <unsigned integer>" 4
.IX Item "max_entropylen (OSSL_DRBG_PARAM_MAX_ENTROPYLEN) <unsigned integer>"
.ie n .IP """min_noncelen"" (\fB\s-1OSSL_DRBG_PARAM_MIN_NONCELEN\s0\fR) <unsigned integer>" 4
.el .IP "``min_noncelen'' (\fB\s-1OSSL_DRBG_PARAM_MIN_NONCELEN\s0\fR) <unsigned integer>" 4
.IX Item "min_noncelen (OSSL_DRBG_PARAM_MIN_NONCELEN) <unsigned integer>"
.ie n .IP """max_noncelen"" (\fB\s-1OSSL_DRBG_PARAM_MAX_NONCELEN\s0\fR) <unsigned integer>" 4
.el .IP "``max_noncelen'' (\fB\s-1OSSL_DRBG_PARAM_MAX_NONCELEN\s0\fR) <unsigned integer>" 4
.IX Item "max_noncelen (OSSL_DRBG_PARAM_MAX_NONCELEN) <unsigned integer>"
.ie n .IP """max_perslen"" (\fB\s-1OSSL_DRBG_PARAM_MAX_PERSLEN\s0\fR) <unsigned integer>" 4
.el .IP "``max_perslen'' (\fB\s-1OSSL_DRBG_PARAM_MAX_PERSLEN\s0\fR) <unsigned integer>" 4
.IX Item "max_perslen (OSSL_DRBG_PARAM_MAX_PERSLEN) <unsigned integer>"
.ie n .IP """max_adinlen"" (\fB\s-1OSSL_DRBG_PARAM_MAX_ADINLEN\s0\fR) <unsigned integer>" 4
.el .IP "``max_adinlen'' (\fB\s-1OSSL_DRBG_PARAM_MAX_ADINLEN\s0\fR) <unsigned integer>" 4
.IX Item "max_adinlen (OSSL_DRBG_PARAM_MAX_ADINLEN) <unsigned integer>"
.ie n .IP """reseed_counter"" (\fB\s-1OSSL_DRBG_PARAM_RESEED_COUNTER\s0\fR) <unsigned integer>" 4
.el .IP "``reseed_counter'' (\fB\s-1OSSL_DRBG_PARAM_RESEED_COUNTER\s0\fR) <unsigned integer>" 4
.IX Item "reseed_counter (OSSL_DRBG_PARAM_RESEED_COUNTER) <unsigned integer>"
.ie n .IP """properties"" (\fB\s-1OSSL_DRBG_PARAM_PROPERTIES\s0\fR) <\s-1UTF8\s0 string>" 4
.el .IP "``properties'' (\fB\s-1OSSL_DRBG_PARAM_PROPERTIES\s0\fR) <\s-1UTF8\s0 string>" 4
.IX Item "properties (OSSL_DRBG_PARAM_PROPERTIES) <UTF8 string>"
.ie n .IP """cipher"" (\fB\s-1OSSL_DRBG_PARAM_CIPHER\s0\fR) <\s-1UTF8\s0 string>" 4
.el .IP "``cipher'' (\fB\s-1OSSL_DRBG_PARAM_CIPHER\s0\fR) <\s-1UTF8\s0 string>" 4
.IX Item "cipher (OSSL_DRBG_PARAM_CIPHER) <UTF8 string>"
.PD
These parameters work as described in \*(L"\s-1PARAMETERS\*(R"\s0 in \s-1\fBEVP_RAND\s0\fR\|(3).
.ie n .IP """use_derivation_function"" (\fB\s-1OSSL_DRBG_PARAM_USE_DF\s0\fR) <integer>" 4
.el .IP "``use_derivation_function'' (\fB\s-1OSSL_DRBG_PARAM_USE_DF\s0\fR) <integer>" 4
.IX Item "use_derivation_function (OSSL_DRBG_PARAM_USE_DF) <integer>"
This Boolean indicates if a derivation function should be used or not.
A nonzero value (the default) uses the derivation function.  A zero value
does not.
.SH "NOTES"
.IX Header "NOTES"
A context for \s-1CTR DRBG\s0 can be obtained by calling:
.PP
.Vb 2
\& EVP_RAND *rand = EVP_RAND_fetch(NULL, "CTR\-DRBG", NULL);
\& EVP_RAND_CTX *rctx = EVP_RAND_CTX_new(rand);
.Ve
.SH "EXAMPLES"
.IX Header "EXAMPLES"
.Vb 5
\& EVP_RAND *rand;
\& EVP_RAND_CTX *rctx;
\& unsigned char bytes[100];
\& OSSL_PARAM params[2], *p = params;
\& unsigned int strength = 128;
\&
\& rand = EVP_RAND_fetch(NULL, "CTR\-DRBG", NULL);
\& rctx = EVP_RAND_CTX_new(rand, NULL);
\& EVP_RAND_free(rand);
\&
\& *p++ = OSSL_PARAM_construct_utf8_string(OSSL_DRBG_PARAM_CIPHER,
\&                                         SN_aes_256_ctr, 0);
\& *p = OSSL_PARAM_construct_end();
\& EVP_RAND_instantiate(rctx, strength, 0, NULL, 0, params);
\&
\& EVP_RAND_generate(rctx, bytes, sizeof(bytes), strength, 0, NULL, 0);
\&
\& EVP_RAND_CTX_free(rctx);
.Ve
.SH "CONFORMING TO"
.IX Header "CONFORMING TO"
\&\s-1NIST SP 800\-90A\s0 and \s-1SP 800\-90B\s0
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\s-1\fBEVP_RAND\s0\fR\|(3),
\&\*(L"\s-1PARAMETERS\*(R"\s0 in \s-1\fBEVP_RAND\s0\fR\|(3)
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2020\-2021 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the Apache License 2.0 (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
<https://www.openssl.org/source/license.html>.