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.\" ========================================================================
.\"
.IX Title "EVP_OPENINIT 3"
.TH EVP_OPENINIT 3 "2023-09-11" "1.1.1w" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
EVP_OpenInit, EVP_OpenUpdate, EVP_OpenFinal \- EVP envelope decryption
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #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);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The \s-1EVP\s0 envelope routines are a high-level interface to envelope
decryption. They decrypt a public key encrypted symmetric key and
then decrypt data using it.
.PP
\&\fBEVP_OpenInit()\fR initializes a cipher context \fBctx\fR for decryption
with cipher \fBtype\fR. It decrypts the encrypted symmetric key of length
\&\fBekl\fR bytes passed in the \fBek\fR parameter using the private key \fBpriv\fR.
The \s-1IV\s0 is supplied in the \fBiv\fR parameter.
.PP
\&\fBEVP_OpenUpdate()\fR and \fBEVP_OpenFinal()\fR have exactly the same properties
as the \fBEVP_DecryptUpdate()\fR and \fBEVP_DecryptFinal()\fR routines, as
documented on the \fBEVP_EncryptInit\fR\|(3) manual
page.
.SH "NOTES"
.IX Header "NOTES"
It is possible to call \fBEVP_OpenInit()\fR twice in the same way as
\&\fBEVP_DecryptInit()\fR. The first call should have \fBpriv\fR set to \s-1NULL\s0
and (after setting any cipher parameters) it should be called again
with \fBtype\fR set to \s-1NULL.\s0
.PP
If the cipher passed in the \fBtype\fR 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.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBEVP_OpenInit()\fR returns 0 on error or a non zero integer (actually the
recovered secret key size) if successful.
.PP
\&\fBEVP_OpenUpdate()\fR returns 1 for success or 0 for failure.
.PP
\&\fBEVP_OpenFinal()\fR returns 0 if the decrypt failed or 1 for success.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBevp\fR\|(7), \fBRAND_bytes\fR\|(3),
\&\fBEVP_EncryptInit\fR\|(3),
\&\fBEVP_SealInit\fR\|(3)
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2000\-2020 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the OpenSSL license (the \*(L"License\*(R").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file \s-1LICENSE\s0 in the source distribution or at
<https://www.openssl.org/source/license.html>.