[#EVP_PKEY_CTX_set_ecdh_cofactor_mode]
= EVP_PKEY_CTX_set_ecdh_cofactor_mode
:mrdocs:

Set whether ECDH key agreement multiplies by the curve cofactor.

== Synopsis

Declared in `<openssl/ec.h>`

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

== Return Value

1 on success, or a negative value on failure.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *ctx*
| Key context configured for ECDH.
| *cofactor_mode*
| 1 to enable cofactor ECDH, 0 to disable, or ‐1 to reset to the default.
|===


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