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.\"
.IX Title "D2I_PRIVATEKEY 3"
.TH D2I_PRIVATEKEY 3 "2023-09-11" "1.1.1w" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.SH "NAME"
d2i_PrivateKey, d2i_PublicKey, d2i_AutoPrivateKey, i2d_PrivateKey, i2d_PublicKey, d2i_PrivateKey_bio, d2i_PrivateKey_fp \&\- 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_PublicKey(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);
\& int i2d_PublicKey(EVP_PKEY *a, unsigned char **pp);
\&
\& EVP_PKEY *d2i_PrivateKey_bio(BIO *bp, EVP_PKEY **a);
\& EVP_PKEY *d2i_PrivateKey_fp(FILE *fp, EVP_PKEY **a)
.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
\&\fB\s-1EVP_PKEY_RSA\s0\fR. An error occurs if the decoded key does not match \fBtype\fR.
\&\fBd2i_PublicKey()\fR does the same for public keys.
.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.
\&\fBi2d_PublicKey()\fR does the same for public keys.
.PP
These functions are similar to the \fBd2i_X509()\fR functions; see \fBd2i_X509\fR\|(3).
.SH "NOTES"
.IX Header "NOTES"
All the functions that operate on data in memory update the data pointer \fI*pp\fR
after a successful operation, just like the other d2i and i2d functions;
see \fBd2i_X509\fR\|(3).
.PP
All these functions use \s-1DER\s0 format and unencrypted keys. Applications wishing
to encrypt or decrypt private keys should use other functions such as
\&\fBd2i_PKCS8PrivateKey()\fR instead.
.PP
If the \fB*a\fR is not \s-1NULL\s0 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.
.PP
To decode a key with type \fB\s-1EVP_PKEY_EC\s0\fR, \fBd2i_PublicKey()\fR requires \fB*a\fR to be
a non-NULL \s-1EVP_PKEY\s0 structure assigned an \s-1EC_KEY\s0 structure referencing the proper
\&\s-1EC_GROUP.\s0
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
The \fBd2i_PrivateKey()\fR, \fBd2i_AutoPrivateKey()\fR, \fBd2i_PrivateKey_bio()\fR, \fBd2i_PrivateKey_fp()\fR,
and \fBd2i_PublicKey()\fR functions return a valid \fB\s-1EVP_KEY\s0\fR structure or \fB\s-1NULL\s0\fR if an
error occurs. The error code can be obtained by calling \fBERR_get_error\fR\|(3).
.PP
\&\fBi2d_PrivateKey()\fR and \fBi2d_PublicKey()\fR return 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\|(7),
\&\fBd2i_PKCS8PrivateKey_bio\fR\|(3)
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2017\-2021 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>.