[#CRYPTO_gcm128_decrypt_ctr32]
= CRYPTO&lowbar;gcm128&lowbar;decrypt&lowbar;ctr32
:mrdocs:

Decrypt ciphertext in GCM using a 32&hyphen;bit CTR stream acceleration callback&period;

== Synopsis

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

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
int
CRYPTO&lowbar;gcm128&lowbar;decrypt&lowbar;ctr32(
    xref:GCM128_CONTEXT-04.adoc[GCM128&lowbar;CONTEXT]* ctx,
    unsigned char const* in,
    unsigned char* out,
    size&lowbar;t len,
    xref:ctr128_f.adoc[ctr128&lowbar;f] stream);
----

== Return Value

1 on success, or 0 on failure&period;

== Parameters

[cols="1,4"]
|===
| Name| Description
| *ctx*
| GCM context ready for decryption&period;
| *in*
| Ciphertext bytes of length `len&period;`
| *out*
| Plaintext buffer of length `len` (may equal `in)&period;`
| *len*
| Number of bytes to decrypt&period;
| *stream*
| Multi&hyphen;block CTR function for the underlying cipher&period;
|===


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