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.\"
.IX Title "d2i_PrivateKey 3"
.TH d2i_PrivateKey 3 2019-12-20 1.0.2u 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
d2i_Private_key, d2i_AutoPrivateKey, i2d_PrivateKey \- decode and encode
functions for reading and saving EVP_PKEY structures.
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/evp.h>
\&
\& EVP_PKEY *d2i_PrivateKey(int type, EVP_PKEY **a, const unsigned char **pp,
\&                          long length);
\& EVP_PKEY *d2i_AutoPrivateKey(EVP_PKEY **a, const unsigned char **pp,
\&                              long length);
\& int i2d_PrivateKey(EVP_PKEY *a, unsigned char **pp);
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
\&\fBd2i_PrivateKey()\fR decodes a private key using algorithm \fBtype\fR. It attempts to
use any key specific format or PKCS#8 unencrypted PrivateKeyInfo format. The
\&\fBtype\fR parameter should be a public key algorithm constant such as
\&\fBEVP_PKEY_RSA\fR. An error occurs if the decoded key does not match \fBtype\fR.
.PP
\&\fBd2i_AutoPrivateKey()\fR is similar to \fBd2i_PrivateKey()\fR except it attempts to
automatically detect the private key format.
.PP
\&\fBi2d_PrivateKey()\fR encodes \fBkey\fR. It uses a key specific format or, if none is
defined for that key type, PKCS#8 unencrypted PrivateKeyInfo format.
.PP
These functions are similar to the \fBd2i_X509()\fR functions, and you should refer to
that page for a detailed description (see \fBd2i_X509\fR\|(3)).
.SH NOTES
.IX Header "NOTES"
All these functions use DER format and unencrypted keys. Applications wishing
to encrypt or decrypt private keys should use other functions such as
\&\fBd2i_PKC8PrivateKey()\fR instead.
.PP
If the \fB*a\fR is not NULL when calling \fBd2i_PrivateKey()\fR or \fBd2i_AutoPrivateKey()\fR
(i.e. an existing structure is being reused) and the key format is PKCS#8
then \fB*a\fR will be freed and replaced on a successful call.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBd2i_PrivateKey()\fR and \fBd2i_AutoPrivateKey()\fR return a valid \fBEVP_KEY\fR structure
or \fBNULL\fR if an error occurs. The error code can be obtained by calling
\&\fBERR_get_error\fR\|(3).
.PP
\&\fBi2d_PrivateKey()\fR returns the number of bytes successfully encoded or a
negative value if an error occurs. The error code can be obtained by calling
\&\fBERR_get_error\fR\|(3).
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBcrypto\fR\|(3),
\&\fBd2i_PKCS8PrivateKey\fR\|(3)