[#EVP_OpenInit]
= EVP_OpenInit
:mrdocs:

Initialize envelope decryption: unwrap `ek` with `priv` and set up `type.`

== Synopsis

Declared in `<openssl/evp.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
int
EVP_OpenInit(
    xref:EVP_CIPHER_CTX.adoc[EVP_CIPHER_CTX]* ctx,
    xref:EVP_CIPHER-07.adoc[EVP_CIPHER] const* type,
    unsigned char const* ek,
    int ekl,
    unsigned char const* iv,
    xref:EVP_PKEY.adoc[EVP_PKEY]* priv);
----

== Return Value

1 on success, or 0 on error.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *ctx*
| Cipher context to initialize for decryption.
| *type*
| Content‐encryption cipher, or NULL to defer until a later call.
| *ek*
| Encrypted content‐encryption key.
| *ekl*
| Length of `ek` in bytes.
| *iv*
| IV for `type,` or NULL if not required yet.
| *priv*
| Recipient private key used to decrypt `ek.`
|===


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