OpenSSL/EC KEY new

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An EC_KEY represents a public key and (optionaly) an associated private key. A new EC_KEY (with no associated curve) can be constructed by calling EC_KEY_new. The reference count for the newly created EC_KEY is initially set to 1. A curve can be associated with the EC_KEY by calling EC_KEY_set_group.

Alternatively a new EC_KEY can be constructed by calling EC_KEY_new_by_curve_name and supplying the nid of the associated curve. Refer to EC_GROUP_new for a description of curve names. This function simply wraps calls to EC_KEY_new and EC_GROUP_new_by_curve_name.

Calling EC_KEY_free decrements the reference count for the EC_KEY object, and if it has dropped to zero then frees the memory associated with it.

EC_KEY_copy copies the contents of the EC_KEY in src into dest.

EC_KEY_dup creates a new EC_KEY object and copies ec_key into it.

EC_KEY_up_ref increments the reference count associated with the EC_KEY object.

EC_KEY_generate_key generates a new public and private key for the supplied eckey object. eckey must have an EC_GROUP object associated with it before calling this function. The private key is a random integer (0 < priv_key < order, where order is the order of the EC_GROUP object). The public key is an EC_POINT on the curve calculated by multiplying the generator for the curve by the private key.

EC_KEY_check_key performs various sanity checks on the EC_KEY object to confirm that it is valid.

EC_KEY_set_public_key_affine_coordinates sets the public key for key based on its affine co-ordinates, i.e. it constructs an EC_POINT object based on the supplied x and y values and sets the public key to be this EC_POINT. It will also performs certain sanity checks on the key to confirm that it is valid.

The functions EC_KEY_get0_group, EC_KEY_set_group, EC_KEY_get0_private_key, EC_KEY_set_private_key, EC_KEY_get0_public_key, and EC_KEY_set_public_key get and set the EC_GROUP object, the private key and the EC_POINT public key for the key respectively.

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.

The functions EC_KEY_get_conv_form and EC_KEY_set_conv_form get and set the point_conversion_form for the key. For a description of point_conversion_forms please refer to EC_POINT_new.

EC_KEY_insert_key_method_data and EC_KEY_get_key_method_data enable the caller to associate arbitary additional data specific to the elliptic curve scheme being used with the EC_KEY object. This data is treated as a "black box" by the ec library. The data to be stored by EC_KEY_insert_key_method_data is provided in the data parameter, which must have have associated functions for duplicating, freeing and "clear_freeing" the data item. If a subsequent EC_KEY_get_key_method_data call is issued, the functions for duplicating, freeing and "clear_freeing" the data item must be provided again, and they must be the same as they were when the data item was inserted.

EC_KEY_set_flags sets the flags in the flags parameter on the EC_KEY object. Any flags that are already set are left set. The currently defined standard flags are EC_FLAG_NON_FIPS_ALLOW and EC_FLAG_FIPS_CHECKED. In addition there is the flag EC_FLAG_COFACTOR_ECDH which is specific to ECDH and is defined in ecdh.h. EC_KEY_get_flags returns the current flags that are set for this EC_KEY. EC_KEY_clear_flags clears the flags indicated by the flags parameter. All other flags are left in their existing state.

EC_KEY_set_asn1_flag sets the asn1_flag on the underlying EC_GROUP object (if set). Refer to EC_GROUP_copy for further information on the asn1_flag.

EC_KEY_precompute_mult stores multiples of the underlying EC_GROUP generator for faster point multiplication. See also EC_POINT_add.

Return Values[edit | edit source]

EC_KEY_new, EC_KEY_new_by_curve_name and EC_KEY_dup return a pointer to the newly created EC_KEY object, or NULL on error.

EC_KEY_get_flags returns the flags associated with the EC_KEY object as an integer.

EC_KEY_copy returns a pointer to the destination key, or NULL on error.

EC_KEY_up_ref, EC_KEY_set_group, EC_KEY_set_private_key, EC_KEY_set_public_key, EC_KEY_precompute_mult, EC_KEY_generate_key, EC_KEY_check_key and EC_KEY_set_public_key_affine_coordinates return 1 on success or 0 on error.

EC_KEY_get0_group returns the EC_GROUP associated with the EC_KEY.

EC_KEY_get0_private_key returns the private key associated with the EC_KEY.

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

EC_KEY_get_conv_form return the point_conversion_form for the EC_KEY.