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.\" ========================================================================
.\"
.IX Title "EVP_RAND-HMAC-DRBG 7ssl"
.TH EVP_RAND-HMAC-DRBG 7ssl 2024-04-28 3.3.0 OpenSSL
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.nh
.SH NAME
EVP_RAND\-HMAC\-DRBG \- The HMAC DRBG EVP_RAND implementation
.SH DESCRIPTION
.IX Header "DESCRIPTION"
Support for the HMAC deterministic random bit generator through the
\&\fBEVP_RAND\fR API.
.SS Identity
.IX Subsection "Identity"
"HMAC-DRBG" 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:
.IP """state"" (\fBOSSL_RAND_PARAM_STATE\fR) <integer>" 4
.IX Item """state"" (OSSL_RAND_PARAM_STATE) <integer>"
.PD 0
.IP """strength"" (\fBOSSL_RAND_PARAM_STRENGTH\fR) <unsigned integer>" 4
.IX Item """strength"" (OSSL_RAND_PARAM_STRENGTH) <unsigned integer>"
.IP """max_request"" (\fBOSSL_RAND_PARAM_MAX_REQUEST\fR) <unsigned integer>" 4
.IX Item """max_request"" (OSSL_RAND_PARAM_MAX_REQUEST) <unsigned integer>"
.IP """reseed_requests"" (\fBOSSL_DRBG_PARAM_RESEED_REQUESTS\fR) <unsigned integer>" 4
.IX Item """reseed_requests"" (OSSL_DRBG_PARAM_RESEED_REQUESTS) <unsigned integer>"
.IP """reseed_time_interval"" (\fBOSSL_DRBG_PARAM_RESEED_TIME_INTERVAL\fR) <integer>" 4
.IX Item """reseed_time_interval"" (OSSL_DRBG_PARAM_RESEED_TIME_INTERVAL) <integer>"
.IP """min_entropylen"" (\fBOSSL_DRBG_PARAM_MIN_ENTROPYLEN\fR) <unsigned integer>" 4
.IX Item """min_entropylen"" (OSSL_DRBG_PARAM_MIN_ENTROPYLEN) <unsigned integer>"
.IP """max_entropylen"" (\fBOSSL_DRBG_PARAM_MAX_ENTROPYLEN\fR) <unsigned integer>" 4
.IX Item """max_entropylen"" (OSSL_DRBG_PARAM_MAX_ENTROPYLEN) <unsigned integer>"
.IP """min_noncelen"" (\fBOSSL_DRBG_PARAM_MIN_NONCELEN\fR) <unsigned integer>" 4
.IX Item """min_noncelen"" (OSSL_DRBG_PARAM_MIN_NONCELEN) <unsigned integer>"
.IP """max_noncelen"" (\fBOSSL_DRBG_PARAM_MAX_NONCELEN\fR) <unsigned integer>" 4
.IX Item """max_noncelen"" (OSSL_DRBG_PARAM_MAX_NONCELEN) <unsigned integer>"
.IP """max_perslen"" (\fBOSSL_DRBG_PARAM_MAX_PERSLEN\fR) <unsigned integer>" 4
.IX Item """max_perslen"" (OSSL_DRBG_PARAM_MAX_PERSLEN) <unsigned integer>"
.IP """max_adinlen"" (\fBOSSL_DRBG_PARAM_MAX_ADINLEN\fR) <unsigned integer>" 4
.IX Item """max_adinlen"" (OSSL_DRBG_PARAM_MAX_ADINLEN) <unsigned integer>"
.IP """reseed_counter"" (\fBOSSL_DRBG_PARAM_RESEED_COUNTER\fR) <unsigned integer>" 4
.IX Item """reseed_counter"" (OSSL_DRBG_PARAM_RESEED_COUNTER) <unsigned integer>"
.IP """properties"" (\fBOSSL_DRBG_PARAM_PROPERTIES\fR) <UTF8 string>" 4
.IX Item """properties"" (OSSL_DRBG_PARAM_PROPERTIES) <UTF8 string>"
.IP """mac"" (\fBOSSL_DRBG_PARAM_MAC\fR) <UTF8 string>" 4
.IX Item """mac"" (OSSL_DRBG_PARAM_MAC) <UTF8 string>"
.IP """digest"" (\fBOSSL_DRBG_PARAM_DIGEST\fR) <UTF8 string>" 4
.IX Item """digest"" (OSSL_DRBG_PARAM_DIGEST) <UTF8 string>"
.PD
These parameters work as described in "PARAMETERS" in \fBEVP_RAND\fR\|(3).
.SH NOTES
.IX Header "NOTES"
When using the FIPS provider, only these digests are permitted (as per
FIPS 140\-3 IG D.R <https://csrc.nist.gov/CSRC/media/Projects/cryptographic-module-validation-program/documents/fips%20140-3/FIPS%20140-3%20IG.pdf>):
.IP SHA\-1 4
.IX Item "SHA-1"
.PD 0
.IP SHA2\-256 4
.IX Item "SHA2-256"
.IP SHA2\-512 4
.IX Item "SHA2-512"
.IP SHA3\-256 4
.IX Item "SHA3-256"
.IP SHA3\-512 4
.IX Item "SHA3-512"
.PD
.PP
A context for HMAC DRBG can be obtained by calling:
.PP
.Vb 2
\& EVP_RAND *rand = EVP_RAND_fetch(NULL, "HMAC\-DRBG", NULL);
\& EVP_RAND_CTX *rctx = EVP_RAND_CTX_new(rand, NULL);
.Ve
.SH EXAMPLES
.IX Header "EXAMPLES"
.Vb 5
\& EVP_RAND *rand;
\& EVP_RAND_CTX *rctx;
\& unsigned char bytes[100];
\& OSSL_PARAM params[3], *p = params;
\& unsigned int strength = 128;
\&
\& rand = EVP_RAND_fetch(NULL, "HMAC\-DRBG", NULL);
\& rctx = EVP_RAND_CTX_new(rand, NULL);
\& EVP_RAND_free(rand);
\&
\& *p++ = OSSL_PARAM_construct_utf8_string(OSSL_DRBG_PARAM_MAC, SN_hmac, 0);
\& *p++ = OSSL_PARAM_construct_utf8_string(OSSL_DRBG_PARAM_DIGEST, SN_sha256, 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"
NIST SP 800\-90A and SP 800\-90B
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBEVP_RAND\fR\|(3),
"PARAMETERS" in \fBEVP_RAND\fR\|(3),
\&\fBopenssl\-fipsinstall\fR\|(1)
.SH HISTORY
.IX Header "HISTORY"
OpenSSL 3.1.1 introduced the \fB\-no_drbg_truncated_digests\fR option to
fipsinstall which restricts the permitted digests when using the FIPS
provider in a complaint manner.  For details refer to
FIPS 140\-3 IG D.R <https://csrc.nist.gov/CSRC/media/Projects/cryptographic-module-validation-program/documents/fips%20140-3/FIPS%20140-3%20IG.pdf>).
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright 2020\-2023 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the Apache License 2.0 (the "License").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file LICENSE in the source distribution or at
<https://www.openssl.org/source/license.html>.