[#CRYPTO_gcm128_decrypt_ctr32]
= CRYPTO_gcm128_decrypt_ctr32
:mrdocs:

Decrypt ciphertext in GCM using a 32‐bit CTR stream acceleration callback.

== Synopsis

Declared in `<openssl/modes.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
int
CRYPTO_gcm128_decrypt_ctr32(
    xref:GCM128_CONTEXT-04.adoc[GCM128_CONTEXT]* ctx,
    unsigned char const* in,
    unsigned char* out,
    size_t len,
    xref:ctr128_f.adoc[ctr128_f] stream);
----

== Return Value

1 on success, or 0 on failure.

== Parameters

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


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