- NAME
- SYNOPSIS
- DESCRIPTION
- NOTES
- RETURN VALUES
- SEE ALSO
- HISTORY
- COPYRIGHT

# NAME

EVP_SKEYMGMT, EVP_SKEYMGMT_fetch, EVP_SKEYMGMT_up_ref, EVP_SKEYMGMT_free, EVP_SKEYMGMT_get0_provider, EVP_SKEYMGMT_is_a, EVP_SKEYMGMT_get0_description, EVP_SKEYMGMT_get0_name, EVP_SKEYMGMT_do_all_provided, EVP_SKEYMGMT_names_do_all, EVP_SKEYMGMT_get0_gen_settable_params, EVP_SKEYMGMT_get0_imp_settable_params - EVP key management routines for opaque symmetric keys

# SYNOPSIS

     #include <openssl/evp.h>

     typedef struct evp_sskeymgmt_st EVP_SKEYMGMT;

     EVP_SKEYMGMT *EVP_SKEYMGMT_fetch(OSSL_LIB_CTX *ctx, const char *algorithm,
                                      const char *properties);
     int EVP_SKEYMGMT_up_ref(EVP_SKEYMGMT *skeymgmt);
     void EVP_SKEYMGMT_free(EVP_SKEYMGMT *skeymgmt);
     const OSSL_PROVIDER *EVP_SKEYMGMT_get0_provider(const EVP_SKEYMGMT *skeymgmt);
     int EVP_SKEYMGMT_is_a(const EVP_SKEYMGMT *skeymgmt, const char *name);
     const char *EVP_SKEYMGMT_get0_name(const EVP_SKEYMGMT *skeymgmt);
     const char *EVP_SKEYMGMT_get0_description(const EVP_SKEYMGMT *skeymgmt);

     void EVP_SKEYMGMT_do_all_provided(OSSL_LIB_CTX *libctx,
                                       void (*fn)(EVP_SKEYMGMT *skeymgmt, void *arg),
                                       void *arg);
     int EVP_SKEYMGMT_names_do_all(const EVP_SKEYMGMT *skeymgmt,
                                   void (*fn)(const char *name, void *data),
                                   void *data);
     const OSSL_PARAM *EVP_SKEYMGMT_get0_gen_settable_params(const EVP_SKEYMGMT *skeymgmt);
     const OSSL_PARAM *EVP_SKEYMGMT_get0_imp_settable_params(const EVP_SKEYMGMT *skeymgmt);

# DESCRIPTION

EVP_SKEYMGMT is a method object that represents symmetric key management implementations for different cryptographic algorithms. This method object provides functionality to allow providers to import key material from the outside, as well as export key material to the outside.

Most of the functionality can only be used internally and has no public interface, this opaque object is simply passed into other functions when needed.

`EVP_SKEYMGMT_fetch()` looks for an algorithm within a provider that has been loaded into the OSSL_LIB_CTX given by ctx, having the name given by algorithm and the properties given by properties.

`EVP_SKEYMGMT_up_ref()` increments the reference count for the given EVP_SKEYMGMT skeymgmt.

`EVP_SKEYMGMT_free()` decrements the reference count for the given EVP_SKEYMGMT skeymgmt, and when the count reaches zero, frees it. If the argument is NULL, nothing is done.

EVP_SKEYMGMT_get0_provider() returns the provider that has this particular implementation.

`EVP_SKEYMGMT_is_a()` checks if skeymgmt is an implementation of an algorithm that's identified by name.

EVP_SKEYMGMT_get0_name() returns the algorithm name from the provided implementation for the given skeymgmt. Note that the skeymgmt may have multiple synonyms associated with it. In this case the first name from the algorithm definition is returned. Ownership of the returned string is retained by the skeymgmt object and should not be freed by the caller.

`EVP_SKEYMGMT_names_do_all()` traverses all names for the skeymgmt, and calls fn with each name and data.

EVP_SKEYMGMT_get0_description() returns a description of the skeymgmt, meant for display and human consumption. The description is at the discretion of the skeymgmt implementation.

`EVP_SKEYMGMT_do_all_provided()` traverses all key skeymgmt implementations by all activated providers in the library context libctx, and for each of the implementations, calls fn with the implementation method and data as arguments.

EVP_SKEYMGMT_get0_gen_settable_params() and EVP_SKEYMGMT_get0_imp_settable_params() get a constant OSSL_PARAM(3) array that describes the settable parameters that can be used with `EVP_SKEY_generate()` and `EVP_SKEY_import()` correspondingly.

# NOTES

`EVP_SKEYMGMT_fetch()` may be called implicitly by other fetching functions, using the same library context and properties. Any other API that uses symmetric keys will typically do this.

# RETURN VALUES

`EVP_SKEYMGMT_fetch()` returns a pointer to the key management implementation represented by an EVP_SKEYMGMT object, or NULL on error.

`EVP_SKEYMGMT_up_ref()` returns 1 on success, or 0 on error.

`EVP_SKEYMGMT_names_do_all()` returns 1 if the callback was called for all names. A return value of 0 means that the callback was not called for any names.

`EVP_SKEYMGMT_free()` doesn't return any value.

EVP_SKEYMGMT_get0_provider() returns a pointer to a provider object, or NULL on error.

`EVP_SKEYMGMT_is_a()` returns 1 if skeymgmt was identifiable, otherwise 0.

EVP_SKEYMGMT_get0_name() returns the algorithm name, or NULL on error.

EVP_SKEYMGMT_get0_description() returns a pointer to a description, or NULL if there isn't one.

# SEE ALSO

EVP_SKEY(3), EVP_MD_fetch(3), OSSL_LIB_CTX(3)

# HISTORY

EVP_SKEYMGMT structure and functions `EVP_SKEYMGMT_fetch()`, `EVP_SKEYMGMT_up_ref()`, `EVP_SKEYMGMT_free()`, EVP_SKEYMGMT_get0_provider(), `EVP_SKEYMGMT_is_a()`, EVP_SKEYMGMT_get0_description(), EVP_SKEYMGMT_get0_name(), `EVP_SKEYMGMT_do_all_provided()`, `EVP_SKEYMGMT_names_do_all()`, EVP_SKEYMGMT_get0_gen_settable_params(), EVP_SKEYMGMT_get0_imp_settable_params() were added in OpenSSL 3.5.

# COPYRIGHT

Copyright 2025 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.