[#CRYPTO_ocb128_init]
= CRYPTO_ocb128_init
:mrdocs:

Initialise an existing OCB128_CONTEXT for the given keys and block functions.

== Synopsis

Declared in `<openssl/modes.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
int
CRYPTO_ocb128_init(
    xref:OCB128_CONTEXT-0a.adoc[OCB128_CONTEXT]* ctx,
    void* keyenc,
    void* keydec,
    xref:block128_f.adoc[block128_f] encrypt,
    xref:block128_f.adoc[block128_f] decrypt,
    xref:ocb128_f.adoc[ocb128_f] stream);
----

== Return Value

1 on success, or 0 on failure.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *ctx*
| Context storage to initialise.
| *keyenc*
| Cipher‐specific expanded key used for encryption‐direction operations.
| *keydec*
| Cipher‐specific expanded key used for decryption‐direction operations.
| *encrypt*
| Block‐encrypt function for the underlying cipher.
| *decrypt*
| Block‐decrypt function for the underlying cipher.
| *stream*
| Optional multi‐block OCB acceleration callback, or NULL.
|===


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