freebsd/secure/lib/libcrypto/man/EVP_OpenInit.3

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.IX Title "EVP_OPENINIT 1"
.TH EVP_OPENINIT 1 "perl v5.6.1" "2000-11-13" "User Contributed Perl Documentation"
.UC
.SH "NAME"
EVP_OpenInit, EVP_OpenUpdate, EVP_OpenFinal \- \s-1EVP\s0 envelope decryption
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/evp.h>
.Ve
.Vb 6
\& 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
\&\fIEVP_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
\&\fIEVP_OpenUpdate()\fR and \fIEVP_OpenFinal()\fR have exactly the same properties
as the \fIEVP_DecryptUpdate()\fR and \fIEVP_DecryptFinal()\fR routines, as 
documented on the EVP_EncryptInit(3) manual
page.
.SH "NOTES"
.IX Header "NOTES"
It is possible to call \fIEVP_OpenInit()\fR twice in the same way as
\&\fIEVP_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"
\&\fIEVP_OpenInit()\fR returns 0 on error or a non zero integer (actually the
recovered secret key size) if successful.
.PP
\&\fIEVP_OpenUpdate()\fR returns 1 for success or 0 for failure.
.PP
\&\fIEVP_OpenFinal()\fR returns 0 if the decrypt failed or 1 for success.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
evp(3), rand(3),
EVP_EncryptInit(3),
EVP_SealInit(3)
.SH "HISTORY"
.IX Header "HISTORY"