[#EVP_CipherInit_ex2]
= EVP_CipherInit_ex2
:mrdocs:

Initialise a cipher context with optional OSSL_PARAM settings.

== Synopsis

Declared in `<openssl/evp.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
int
EVP_CipherInit_ex2(
    xref:EVP_CIPHER_CTX.adoc[EVP_CIPHER_CTX]* ctx,
    xref:EVP_CIPHER-07.adoc[EVP_CIPHER] const* cipher,
    unsigned char const* key,
    unsigned char const* iv,
    int enc,
    xref:OSSL_PARAM.adoc[OSSL_PARAM] const params[]);
----

== Return Value

1 on success, or 0 on failure.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *ctx*
| Cipher context to initialise.
| *cipher*
| Cipher algorithm, or NULL to reuse the one already in `ctx.`
| *key*
| Key bytes, or NULL to set later.
| *iv*
| IV/nonce bytes, or NULL when not yet available / not required.
| *enc*
| 1 to encrypt, 0 to decrypt, or ‐1 to leave the prior direction.
| *params*
| Optional parameter array terminated by OSSL_PARAM_END, or NULL.
|===


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