[#CRYPTO_gcm128_tag]
= CRYPTO&lowbar;gcm128&lowbar;tag
:mrdocs:

Write the computed GCM authentication tag into `tag&period;`

== Synopsis

Declared in `&lt;openssl&sol;modes&period;h&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
void
CRYPTO&lowbar;gcm128&lowbar;tag(
    xref:GCM128_CONTEXT-04.adoc[GCM128&lowbar;CONTEXT]* ctx,
    unsigned char* tag,
    size&lowbar;t len);
----

== Parameters

[cols="1,4"]
|===
| Name| Description
| *ctx*
| GCM context after encryption (typically after CRYPTO&lowbar;gcm128&lowbar;finish with NULL tag)&period;
| *tag*
| Destination buffer for the tag&period;
| *len*
| Number of tag bytes to write (commonly 16)&period;
|===


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