Manpages - d2i_PrivateKey.3ssl

Table of Contents


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


#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)


d2i_PrivateKey() decodes a private key using algorithm type. It attempts to use any key specific format or PKCS#8 unencrypted PrivateKeyInfo format. The type parameter should be a public key algorithm constant such as EVP_PKEY_RSA. An error occurs if the decoded key does not match type. d2i_PublicKey() does the same for public keys.

d2i_AutoPrivateKey() is similar to d2i_PrivateKey() except it attempts to automatically detect the private key format.

i2d_PrivateKey() encodes key. It uses a key specific format or, if none is defined for that key type, PKCS#8 unencrypted PrivateKeyInfo format. i2d_PublicKey() does the same for public keys.

These functions are similar to the d2i_X509() functions; see d2i_X509 (3).


All the functions that operate on data in memory update the data pointer *pp after a successful operation, just like the other d2i and i2d functions; see d2i_X509 (3).

All these functions use DER format and unencrypted keys. Applications wishing to encrypt or decrypt private keys should use other functions such as d2i_PKCS8PrivateKey() instead.

If the *a is not NULL when calling d2i_PrivateKey() or d2i_AutoPrivateKey() (i.e. an existing structure is being reused) and the key format is PKCS#8 then *a will be freed and replaced on a successful call.

To decode a key with type EVP_PKEY_EC, d2i_PublicKey() requires *a to be a non-NULL EVP_PKEY structure assigned an EC_KEY structure referencing the proper EC_GROUP.


The d2i_PrivateKey(), d2i_AutoPrivateKey(), d2i_PrivateKey_bio(), d2i_PrivateKey_fp(), and d2i_PublicKey() functions return a valid EVP_KEY structure or NULL if an error occurs. The error code can be obtained by calling ERR_get_error (3).

i2d_PrivateKey() and i2d_PublicKey() return the number of bytes successfully encoded or a negative value if an error occurs. The error code can be obtained by calling ERR_get_error (3).


crypto (7), d2i_PKCS8PrivateKey_bio (3)


Copyright 2017-2021 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (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

Author: dt

Created: 2022-02-20 Sun 15:02