[#ASN1_item_verify_ex]
= ASN1_item_verify_ex
:mrdocs:

Verify `signature` over the DER encoding of `data` described by `it.`

== Synopsis

Declared in `<openssl/asn1.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
int
ASN1_item_verify_ex(
    xref:ASN1_ITEM.adoc[ASN1_ITEM] const* it,
    xref:X509_ALGOR.adoc[X509_ALGOR] const* alg,
    xref:ASN1_BIT_STRING.adoc[ASN1_BIT_STRING] const* signature,
    void const* data,
    xref:ASN1_OCTET_STRING.adoc[ASN1_OCTET_STRING] const* id,
    xref:EVP_PKEY.adoc[EVP_PKEY]* pkey,
    xref:OSSL_LIB_CTX.adoc[OSSL_LIB_CTX]* libctx,
    char const* propq);
----

== Return Value

1 on success, 0 on failure, or ‐1 on a more serious error.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *it*
| ASN.1 item describing the type of `data.`
| *alg*
| Signature AlgorithmIdentifier.
| *signature*
| BIT STRING holding the signature bytes.
| *data*
| Object whose DER encoding is verified.
| *id*
| Optional ASN.1 OCTET STRING identity / SM2‐id parameter, or NULL.
| *pkey*
| Public key used to verify the signature.
| *libctx*
| Library context for algorithm fetches, or NULL for the default.
| *propq*
| Property query for algorithm fetches, or NULL.
|===


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