[#CRYPTO_128_unwrap]
= CRYPTO_128_unwrap
:mrdocs:

Unwrap a key with AES Key Wrap (RFC 3394) using `block.`

== Synopsis

Declared in `<openssl/modes.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
size_t
CRYPTO_128_unwrap(
    void* key,
    unsigned char const* iv,
    unsigned char* out,
    unsigned char const* in,
    size_t inlen,
    xref:block128_f.adoc[block128_f] block);
----

== Return Value

Length of unwrapped data written to `out,` or 0 on error (including IV mismatch).

== Parameters

[cols="1,4"]
|===
| Name| Description
| *key*
| Cipher‐specific expanded key for `block.`
| *iv*
| Optional expected 8‐byte IV, or NULL for the RFC 3394 default IV.
| *out*
| Buffer for the unwrapped key (at least `inlen` ‐ 8 bytes).
| *in*
| Wrapped key material as n 64‐bit blocks with n >= 2.
| *inlen*
| Length of `in` in bytes (multiple of 8, at least 16).
| *block*
| Block‐decrypt function used by the unwrap algorithm.
|===


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