[#HMAC_Init]
= HMAC_Init
:mrdocs:

Initialize an HMAC context with a key and digest (legacy).

== Synopsis

Declared in `<openssl/hmac.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
[[deprecated]]
int
HMAC_Init(
    xref:HMAC_CTX.adoc[HMAC_CTX]* ctx,
    void const* key,
    int len,
    xref:EVP_MD.adoc[EVP_MD] const* md);
----

[WARNING]
====
https://en.cppreference.com/cpp/language/attributes/deprecated[Deprecated^]. Use of this entity is allowed but discouraged.
====
== Return Value

1 on success, or 0 on error.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *ctx*
| HMAC context to initialize.
| *key*
| HMAC key material.
| *len*
| Length of `key` in bytes.
| *md*
| Message digest to use, or NULL to keep the current digest.
|===


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