[#EVP_PKEY_CTX_set_hkdf_md]
= EVP_PKEY_CTX_set_hkdf_md
:mrdocs:

Set the message digest used by the HKDF extract/expand stages.

== Synopsis

Declared in `<openssl/kdf.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
int
EVP_PKEY_CTX_set_hkdf_md(
    xref:EVP_PKEY_CTX.adoc[EVP_PKEY_CTX]* ctx,
    xref:EVP_MD.adoc[EVP_MD] const* md);
----

== Return Value

1 on success, or a negative value on error.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *ctx*
| Context configured for the HKDF KDF.
| *md*
| Digest algorithm (for example EVP_sha256()).
|===


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