---
name: "EVP_OpenInit"
section: "3ssl"
platform: "linux"
package: "openssl"
version: "3.6.5-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/EVP_OpenInit"
---

# EVP\_OpenInit(3ssl)

EVP envelope decryption

## NAME

EVP\_OpenInit, EVP\_OpenUpdate, EVP\_OpenFinal - EVP envelope decryption

## SYNOPSIS

```
 #include <openssl/evp.h>
 int EVP_OpenInit(EVP_CIPHER_CTX *ctx, EVP_CIPHER *type, unsigned char *ek,
                  int ekl, unsigned char *iv, EVP_PKEY *priv);
 int EVP_OpenUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
                    int *outl, unsigned char *in, int inl);
 int EVP_OpenFinal(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl);
```

## DESCRIPTION

The EVP envelope routines are a high-level interface to envelope decryption. They decrypt a public key encrypted symmetric key and then decrypt data using it.

**EVP\_OpenInit()** initializes a cipher context **ctx** for decryption with cipher **type**. It decrypts the encrypted symmetric key of length **ekl** bytes passed in the **ek** parameter using the private key **priv**. The IV is supplied in the **iv** parameter.

**EVP\_OpenUpdate()** and **EVP\_OpenFinal()** have exactly the same properties as the **EVP\_DecryptUpdate()** and **EVP\_DecryptFinal()** routines, as documented on the **EVP\_EncryptInit**(3) manual page.

## NOTES

It is possible to call **EVP\_OpenInit()** twice in the same way as **EVP\_DecryptInit()**. The first call should have **priv** set to NULL and (after setting any cipher parameters) it should be called again with **type** set to NULL.

If the cipher passed in the **type** parameter is a variable length cipher then the key length will be set to the value of the recovered key length. If the cipher is a fixed length cipher then the recovered key length must match the fixed cipher length.

## RETURN VALUES

**EVP\_OpenInit()** returns 0 on error or a non zero integer (actually the recovered secret key size) if successful.

**EVP\_OpenUpdate()** returns 1 for success or 0 for failure.

**EVP\_OpenFinal()** returns 0 if the decrypt failed or 1 for success.

## SEE ALSO

**evp**(7), **RAND\_bytes**(3), **EVP\_EncryptInit**(3), **EVP\_SealInit**(3)

## COPYRIGHT

Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License").  You may not use this file except in compliance with the License.  You can obtain a copy in the file LICENSE in the source distribution or at \<https://www.openssl.org/source/license.html\>.