[#EVP_PKEY_set_ex_data]
= EVP_PKEY_set_ex_data
:mrdocs:

Store application‐specific data on an EVP_PKEY at a CRYPTO ex_data index.

== Synopsis

Declared in `<openssl/evp.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
int
EVP_PKEY_set_ex_data(
    xref:EVP_PKEY.adoc[EVP_PKEY]* key,
    int idx,
    void* arg);
----

== Return Value

1 on success, or 0 on failure.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *key*
| Key that owns the ex_data table.
| *idx*
| Index obtained from EVP_PKEY_get_ex_new_index() (or a reserved index).
| *arg*
| Pointer to store; ownership remains with the caller unless free callbacks manage it.
|===


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