[#EVP_PKEY_asn1_set_param]
= EVP_PKEY_asn1_set_param
:mrdocs:

Install parameter encode/decode, missing, copy, compare, and print callbacks on an ASN.1 method.

== Synopsis

Declared in `<openssl/evp.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
void
EVP_PKEY_asn1_set_param(
    xref:EVP_PKEY_ASN1_METHOD.adoc[EVP_PKEY_ASN1_METHOD]* ameth,
    int(* param_decode)(xref:EVP_PKEY.adoc[EVP_PKEY]*, unsigned char const**, int),
    int(* param_encode)(xref:EVP_PKEY.adoc[EVP_PKEY] const*, unsigned char**),
    int(* param_missing)(xref:EVP_PKEY.adoc[EVP_PKEY] const*),
    int(* param_copy)(xref:EVP_PKEY.adoc[EVP_PKEY]*, xref:EVP_PKEY.adoc[EVP_PKEY] const*),
    int(* param_cmp)(xref:EVP_PKEY.adoc[EVP_PKEY] const*, xref:EVP_PKEY.adoc[EVP_PKEY] const*),
    int(* param_print)(xref:BIO.adoc[BIO]*, xref:EVP_PKEY.adoc[EVP_PKEY] const*, int, xref:ASN1_PCTX.adoc[ASN1_PCTX]*));
----

== Parameters

[cols="1,4"]
|===
| Name| Description
| *ameth*
| ASN.1 method being customized.
| *param_decode*
| Decode algorithm parameters from DER into `pkey.`
| *param_encode*
| Encode algorithm parameters from `pkey` to DER.
| *param_missing*
| Return nonzero if `pk` lacks required parameters.
| *param_copy*
| Copy parameters from `from` into `to.`
| *param_cmp*
| Compare parameters of two keys (1 match, 0 differ, negative on error).
| *param_print*
| Print parameters to a BIO.
|===


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