EVP_KDF-X963 - The X9.63-2001 EVP_KDF implementation
The EVP_KDF-X963 algorithm implements the key derivation function (X963KDF).
X963KDF is used by Cryptographic Message Syntax (CMS) for EC KeyAgreement, to
derive a key using input such as a shared secret key and shared info.
"X963KDF" is the name for this implementation; it can be used with the
EVP_KDF_fetch() function.
The supported parameters are:
- "properties" (OSSL_KDF_PARAM_PROPERTIES) <UTF8
string>
- "digest" (OSSL_KDF_PARAM_DIGEST) <UTF8 string>
- These parameters work as described in "PARAMETERS" in
EVP_KDF(3).
- "key" (OSSL_KDF_PARAM_KEY) <octet string>
- The shared secret used for key derivation. This parameter sets the
secret.
- "info" (OSSL_KDF_PARAM_INFO) <octet string>
- This parameter specifies an optional value for shared info.
X963KDF is very similar to the SSKDF that uses a digest as the auxiliary
function, X963KDF appends the counter to the secret, whereas SSKDF prepends
the counter.
A context for X963KDF can be obtained by calling:
EVP_KDF *kdf = EVP_KDF_fetch(NULL, "X963KDF", NULL);
EVP_KDF_CTX *kctx = EVP_KDF_CTX_new(kdf);
The output length of an X963KDF is specified via the keylen
parameter to the EVP_KDF_derive(3) function.
This example derives 10 bytes, with the secret key "secret" and
sharedinfo value "label":
EVP_KDF *kdf;
EVP_KDF_CTX *kctx;
unsigned char out[10];
OSSL_PARAM params[4], *p = params;
kdf = EVP_KDF_fetch(NULL, "X963KDF", NULL);
kctx = EVP_KDF_CTX_new(kdf);
EVP_KDF_free(kdf);
*p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST,
SN_sha256, strlen(SN_sha256));
*p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SECRET,
"secret", (size_t)6);
*p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO,
"label", (size_t)5);
*p = OSSL_PARAM_construct_end();
if (EVP_KDF_derive(kctx, out, sizeof(out), params) <= 0) {
error("EVP_KDF_derive");
}
EVP_KDF_CTX_free(kctx);
"SEC 1: Elliptic Curve Cryptography"
EVP_KDF(3), EVP_KDF_CTX_new(3), EVP_KDF_CTX_free(3),
EVP_KDF_CTX_set_params(3), EVP_KDF_CTX_get_kdf_size(3),
EVP_KDF_derive(3), "PARAMETERS" in EVP_KDF(3)
This functionality was added in OpenSSL 3.0.
Copyright 2019-2021 The OpenSSL Project Authors. All Rights Reserved.
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>.