[#CRYPTO_cfb128_encrypt]
= CRYPTO_cfb128_encrypt
:mrdocs:

Encrypt or decrypt with a 128‐bit block cipher in full‐block CFB mode.

== Synopsis

Declared in `<openssl/modes.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
void
CRYPTO_cfb128_encrypt(
    unsigned char const* in,
    unsigned char* out,
    size_t len,
    void const* key,
    unsigned char ivec[],
    int* num,
    int enc,
    xref:block128_f.adoc[block128_f] block);
----

== Parameters

[cols="1,4"]
|===
| Name| Description
| *in*
| Input bytes of length `len.`
| *out*
| Output buffer of length `len` (may equal `in).`
| *len*
| Number of bytes to process.
| *key*
| Cipher‐specific expanded key for `block.`
| *ivec*
| 16‐byte IV / feedback block updated in place.
| *num*
| Offset into the current CFB block (updated; typically starts at 0).
| *enc*
| Non‐zero to encrypt, zero to decrypt.
| *block*
| Block‐encrypt function for the underlying cipher.
|===


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