- NAME
- SYNOPSIS
- DESCRIPTION
- RETURN VALUES
- SEE ALSO

# NAME

i2d_ECPrivateKey, d2i_ECPrivate_key - Encode and decode functions for saving and reading EC_KEY structures

# SYNOPSIS

     #include <openssl/ec.h>

     EC_KEY *d2i_ECPrivateKey(EC_KEY **key, const unsigned char **in, long len);
     int i2d_ECPrivateKey(EC_KEY *key, unsigned char **out);

     unsigned int EC_KEY_get_enc_flags(const EC_KEY *key);
     void EC_KEY_set_enc_flags(EC_KEY *eckey, unsigned int flags);

# DESCRIPTION

The ECPrivateKey encode and decode routines encode and parse an EC_KEY structure into a binary format (ASN.1 DER) and back again.

These functions are similar to the `d2i_X509()` functions, and you should refer to that page for a detailed description (see d2i_X509).

The format of the external representation of the public key written by i2d_ECPrivateKey (such as whether it is stored in a compressed form or not) is described by the point_conversion_form. See EC_GROUP_copy for a description of point_conversion_form.

When reading a private key encoded without an associated public key (e.g. if EC_PKEY_NO_PUBKEY has been used - see below), then d2i_ECPrivateKey generates the missing public key automatically. Private keys encoded without parameters (e.g. if EC_PKEY_NO_PARAMETERS has been used - see below) cannot be loaded using d2i_ECPrivateKey.

The functions EC_KEY_get_enc_flags and EC_KEY_set_enc_flags get and set the value of the encoding flags for the key. There are two encoding flags currently defined - EC_PKEY_NO_PARAMETERS and EC_PKEY_NO_PUBKEY. These flags define the behaviour of how the key is converted into ASN1 in a call to i2d_ECPrivateKey. If EC_PKEY_NO_PARAMETERS is set then the public parameters for the curve are not encoded along with the private key. If EC_PKEY_NO_PUBKEY is set then the public key is not encoded along with the private key.

# RETURN VALUES

`d2i_ECPrivateKey()` returns a valid EC_KEY structure or NULL if an error occurs. The error code that can be obtained by ERR_get_error.

`i2d_ECPrivateKey()` returns the number of bytes successfully encoded or a negative value if an error occurs. The error code can be obtained by ERR_get_error.

EC_KEY_get_enc_flags returns the value of the current encoding flags for the EC_KEY.

# SEE ALSO

crypto, ec, EC_GROUP_new, EC_GROUP_copy, EC_POINT_new, EC_POINT_add, EC_GFp_simple_method, d2i_ECPKParameters, d2i_ECPrivateKey