.\" Automatically generated by Pod::Man 4.14 (Pod::Simple 3.40) .\" .\" Standard preamble: .\" ======================================================================== .de Sp \" Vertical space (when we can't use .PP) .if t .sp .5v .if n .sp .. .de Vb \" Begin verbatim text .ft CW .nf .ne \\$1 .. .de Ve \" End verbatim text .ft R .fi .. .\" Set up some character translations and predefined strings. \*(-- will .\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left .\" double quote, and \*(R" will give a right double quote. \*(C+ will .\" give a nicer C++. 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Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH "NAME" EVP_KDF\-KB \- The Key\-Based EVP_KDF implementation .SH "DESCRIPTION" .IX Header "DESCRIPTION" The \s-1EVP_KDF\-KB\s0 algorithm implements the Key-Based key derivation function (\s-1KBKDF\s0). \s-1KBKDF\s0 derives a key from repeated application of a keyed \s-1MAC\s0 to an input secret (and other optional values). .SS "Identity" .IX Subsection "Identity" \&\*(L"\s-1KBKDF\*(R"\s0 is the name for this implementation; it can be used with the \&\fBEVP_KDF_fetch()\fR function. .SS "Supported parameters" .IX Subsection "Supported parameters" The supported parameters are: .ie n .IP """mode"" (\fB\s-1OSSL_KDF_PARAM_MODE\s0\fR) <\s-1UTF8\s0 string>" 4 .el .IP "``mode'' (\fB\s-1OSSL_KDF_PARAM_MODE\s0\fR) <\s-1UTF8\s0 string>" 4 .IX Item "mode (OSSL_KDF_PARAM_MODE) " The mode parameter determines which flavor of \s-1KBKDF\s0 to use \- currently the choices are \*(L"counter\*(R" and \*(L"feedback\*(R". \*(L"counter\*(R" is the default, and will be used if unspecified. .ie n .IP """mac"" (\fB\s-1OSSL_KDF_PARAM_MAC\s0\fR) <\s-1UTF8\s0 string>" 4 .el .IP "``mac'' (\fB\s-1OSSL_KDF_PARAM_MAC\s0\fR) <\s-1UTF8\s0 string>" 4 .IX Item "mac (OSSL_KDF_PARAM_MAC) " The value is either \s-1CMAC\s0 or \s-1HMAC.\s0 .ie n .IP """digest"" (\fB\s-1OSSL_KDF_PARAM_DIGEST\s0\fR) <\s-1UTF8\s0 string>" 4 .el .IP "``digest'' (\fB\s-1OSSL_KDF_PARAM_DIGEST\s0\fR) <\s-1UTF8\s0 string>" 4 .IX Item "digest (OSSL_KDF_PARAM_DIGEST) " .PD 0 .ie n .IP """cipher"" (\fB\s-1OSSL_KDF_PARAM_CIPHER\s0\fR) <\s-1UTF8\s0 string>" 4 .el .IP "``cipher'' (\fB\s-1OSSL_KDF_PARAM_CIPHER\s0\fR) <\s-1UTF8\s0 string>" 4 .IX Item "cipher (OSSL_KDF_PARAM_CIPHER) " .ie n .IP """properties"" (\fB\s-1OSSL_KDF_PARAM_PROPERTIES\s0\fR) <\s-1UTF8\s0 string>" 4 .el .IP "``properties'' (\fB\s-1OSSL_KDF_PARAM_PROPERTIES\s0\fR) <\s-1UTF8\s0 string>" 4 .IX Item "properties (OSSL_KDF_PARAM_PROPERTIES) " .ie n .IP """key"" (\fB\s-1OSSL_KDF_PARAM_KEY\s0\fR) " 4 .el .IP "``key'' (\fB\s-1OSSL_KDF_PARAM_KEY\s0\fR) " 4 .IX Item "key (OSSL_KDF_PARAM_KEY) " .ie n .IP """salt"" (\fB\s-1OSSL_KDF_PARAM_SALT\s0\fR) " 4 .el .IP "``salt'' (\fB\s-1OSSL_KDF_PARAM_SALT\s0\fR) " 4 .IX Item "salt (OSSL_KDF_PARAM_SALT) " .IP """info (\fB\s-1OSSL_KDF_PARAM_INFO\s0\fR) " 4 .IX Item """info (OSSL_KDF_PARAM_INFO) " .ie n .IP """seed"" (\fB\s-1OSSL_KDF_PARAM_SEED\s0\fR) " 4 .el .IP "``seed'' (\fB\s-1OSSL_KDF_PARAM_SEED\s0\fR) " 4 .IX Item "seed (OSSL_KDF_PARAM_SEED) " .PD The seed parameter is unused in counter mode. .ie n .IP """use-l"" (\fB\s-1OSSL_KDF_PARAM_KBKDF_USE_L\s0\fR) " 4 .el .IP "``use-l'' (\fB\s-1OSSL_KDF_PARAM_KBKDF_USE_L\s0\fR) " 4 .IX Item "use-l (OSSL_KDF_PARAM_KBKDF_USE_L) " Set to \fB0\fR to disable use of the optional Fixed Input data 'L' (see \s-1SP800\-108\s0). The default value of \fB1\fR will be used if unspecified. .ie n .IP """use-separator"" (\fB\s-1OSSL_KDF_PARAM_KBKDF_USE_SEPARATOR\s0\fR) " 4 .el .IP "``use-separator'' (\fB\s-1OSSL_KDF_PARAM_KBKDF_USE_SEPARATOR\s0\fR) " 4 .IX Item "use-separator (OSSL_KDF_PARAM_KBKDF_USE_SEPARATOR) " Set to \fB0\fR to disable use of the optional Fixed Input data 'zero separator' (see \s-1SP800\-108\s0) that is placed between the Label and Context. The default value of \fB1\fR will be used if unspecified. .PP Depending on whether mac is \s-1CMAC\s0 or \s-1HMAC,\s0 either digest or cipher is required (respectively) and the other is unused. .PP The parameters key, salt, info, and seed correspond to \s-1KI,\s0 Label, Context, and \&\s-1IV\s0 (respectively) in \s-1SP800\-108.\s0 As in that document, salt, info, and seed are optional and may be omitted. .PP \&\*(L"mac\*(R", \*(L"digest\*(R", cipher\*(L" and \*(R"properties" are described in \&\*(L"\s-1PARAMETERS\*(R"\s0 in \s-1\fBEVP_KDF\s0\fR\|(3). .SH "NOTES" .IX Header "NOTES" A context for \s-1KBKDF\s0 can be obtained by calling: .PP .Vb 2 \& EVP_KDF *kdf = EVP_KDF_fetch(NULL, "KBKDF", NULL); \& EVP_KDF_CTX *kctx = EVP_KDF_CTX_new(kdf); .Ve .PP The output length of an \s-1KBKDF\s0 is specified via the \f(CW\*(C`keylen\*(C'\fR parameter to the \fBEVP_KDF_derive\fR\|(3) function. .PP Note that currently OpenSSL only implements counter and feedback modes. Other variants may be supported in the future. .SH "EXAMPLES" .IX Header "EXAMPLES" This example derives 10 bytes using \s-1COUNTER\-HMAC\-SHA256,\s0 with \s-1KI\s0 \*(L"secret\*(R", Label \*(L"label\*(R", and Context \*(L"context\*(R". .PP .Vb 4 \& EVP_KDF *kdf; \& EVP_KDF_CTX *kctx; \& unsigned char out[10]; \& OSSL_PARAM params[6], *p = params; \& \& kdf = EVP_KDF_fetch(NULL, "KBKDF", NULL); \& kctx = EVP_KDF_CTX_new(kdf); \& EVP_KDF_free(kdf); \& \& *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST, \& "SHA2\-256", 0); \& *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_MAC, \& "HMAC", 0); \& *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_KEY, \& "secret", strlen("secret")); \& *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SALT, \& "label", strlen("label")); \& *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO, \& "context", strlen("context")); \& *p = OSSL_PARAM_construct_end(); \& if (EVP_KDF_derive(kctx, out, sizeof(out), params) <= 0) \& error("EVP_KDF_derive"); \& \& EVP_KDF_CTX_free(kctx); .Ve .PP This example derives 10 bytes using \s-1FEEDBACK\-CMAC\-AES256,\s0 with \s-1KI\s0 \*(L"secret\*(R", Label \*(L"label\*(R", and \s-1IV\s0 \*(L"sixteen bytes iv\*(R". .PP .Vb 5 \& EVP_KDF *kdf; \& EVP_KDF_CTX *kctx; \& unsigned char out[10]; \& OSSL_PARAM params[8], *p = params; \& unsigned char *iv = "sixteen bytes iv"; \& \& kdf = EVP_KDF_fetch(NULL, "KBKDF", NULL); \& kctx = EVP_KDF_CTX_new(kdf); \& EVP_KDF_free(kdf); \& \& *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_CIPHER, "AES256", 0); \& *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_MAC, "CMAC", 0); \& *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_MODE, "FEEDBACK", 0); \& *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_KEY, \& "secret", strlen("secret")); \& *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SALT, \& "label", strlen("label")); \& *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO, \& "context", strlen("context")); \& *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SEED, \& iv, strlen(iv)); \& *p = OSSL_PARAM_construct_end(); \& if (EVP_KDF_derive(kctx, out, sizeof(out), params) <= 0) \& error("EVP_KDF_derive"); \& \& EVP_KDF_CTX_free(kctx); .Ve .SH "CONFORMING TO" .IX Header "CONFORMING TO" \&\s-1NIST SP800\-108, IETF RFC 6803, IETF RFC 8009.\s0 .SH "SEE ALSO" .IX Header "SEE ALSO" \&\s-1\fBEVP_KDF\s0\fR\|(3), \&\fBEVP_KDF_CTX_free\fR\|(3), \&\fBEVP_KDF_CTX_get_kdf_size\fR\|(3), \&\fBEVP_KDF_derive\fR\|(3), \&\*(L"\s-1PARAMETERS\*(R"\s0 in \s-1\fBEVP_KDF\s0\fR\|(3) .SH "HISTORY" .IX Header "HISTORY" This functionality was added in OpenSSL 3.0. .SH "COPYRIGHT" .IX Header "COPYRIGHT" Copyright 2019\-2021 The OpenSSL Project Authors. All Rights Reserved. Copyright 2019 Red Hat, Inc. .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 .