[#EVP_PKEY_CTX_get_ecdh_kdf_outlen]
= EVP_PKEY_CTX_get_ecdh_kdf_outlen
:mrdocs:

Get the ECDH key‐derivation output length from a key‐exchange context.

== Synopsis

Declared in `<openssl/ec.h>`

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

== Return Value

1 on success, or a negative value on failure.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *ctx*
| EVP_PKEY context configured for ECDH with a KDF.
| *len*
| Receives the derived‐key length in bytes.
|===


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