[#EVP_CipherInit_ex]
= EVP_CipherInit_ex
:mrdocs:

Initialise `ctx` for encryption or decryption with `cipher.`

== Synopsis

Declared in `<openssl/evp.h>`

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

== Return Value

1 on success, or 0 on error.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *ctx*
| Cipher context to initialise.
| *cipher*
| Cipher algorithm, or NULL to keep the current cipher and change key/IV/dir.
| *impl*
| Legacy ENGINE, or NULL for the default implementation.
| *key*
| Raw key bytes, or NULL to set later.
| *iv*
| IV/nonce bytes, or NULL when not required / set later.
| *enc*
| 1 to encrypt, 0 to decrypt, or ‐1 to leave the direction unchanged.
|===


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