[#CRYPTO_ocb128_finish]
= CRYPTO_ocb128_finish
:mrdocs:

Finalise OCB and verify a received authentication tag.

== Synopsis

Declared in `<openssl/modes.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
int
CRYPTO_ocb128_finish(
    xref:OCB128_CONTEXT-0a.adoc[OCB128_CONTEXT]* ctx,
    unsigned char const* tag,
    size_t len);
----

== Return Value

0 if `tag` matches, a non‐zero value if it does not, or ‐1 if `len` is invalid.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *ctx*
| OCB context after encrypt/decrypt (and AAD) processing.
| *tag*
| Expected authentication tag to compare.
| *len*
| Length of `tag` in bytes (1–16).
|===


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