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       OSSL_ENCODER_CTX_new_for_pkey, OSSL_ENCODER_CTX_set_cipher,
       OSSL_ENCODER_CTX_set_passphrase,	OSSL_ENCODER_CTX_set_pem_password_cb,
       OSSL_ENCODER_CTX_set_passphrase_cb, OSSL_ENCODER_CTX_set_passphrase_ui
       - Encoder routines to encode EVP_PKEYs

	#include <openssl/encoder.h>

	OSSL_ENCODER_CTX_new_for_pkey(const EVP_PKEY *pkey, int	selection,
				      const char *output_type,
				      const char *output_structure,
				      const char *propquery);

					const char *cipher_name,
					const char *propquery);
	int OSSL_ENCODER_CTX_set_passphrase(OSSL_ENCODER_CTX *ctx,
					    const unsigned char	*kstr,
					    size_t klen);
	int OSSL_ENCODER_CTX_set_pem_password_cb(OSSL_ENCODER_CTX *ctx,
						 pem_password_cb *cb, void *cbarg);
	int OSSL_ENCODER_CTX_set_passphrase_ui(OSSL_ENCODER_CTX	*ctx,
					       const UI_METHOD *ui_method,
					       void *ui_data);
	int OSSL_ENCODER_CTX_set_passphrase_cb(OSSL_ENCODER_CTX	*ctx,
					       void *cbarg);

       OSSL_ENCODER_CTX_new_for_pkey() is a utility function that creates a
       OSSL_ENCODER_CTX, finds all applicable encoder implementations and sets
       them up,	so almost all the caller has to	do next	is call	functions like
       OSSL_ENCODER_to_bio(3).	output_type determines the final output
       encoding, and selection can be used to select what parts	of the pkey
       should be included in the output.  output_type is further discussed in
       "Output types" below, and selection is further described	in

       Internally, OSSL_ENCODER_CTX_new_for_pkey() uses	the names from the
       EVP_KEYMGMT(3) implementation associated	with pkey to build a list of
       applicable encoder implementations that are used	to process the pkey
       into the	encoding named by output_type, with the	outermost structure
       named by	output_structure if that's relevant.  All these
       implementations are implicitly fetched, with propquery for finer

       If no suitable encoder implementation is	found,
       OSSL_ENCODER_CTX_new_for_pkey() still creates a OSSL_ENCODER_CTX, but
       with no associated encoder (OSSL_ENCODER_CTX_get_num_encoders(3)
       returns zero).  This helps the caller to	distinguish between an error
       when creating the OSSL_ENCODER_CTX and missing encoder implementation,
       and allows it to	act accordingly.

       OSSL_ENCODER_CTX_set_cipher() tells the implementation what cipher
       should be used to encrypt encoded keys.	The cipher is given by name
       cipher_name.  The interpretation	of that	cipher_name is implementation
       dependent.  The implementation may implement the	cipher directly	itself
       or by other implementations, or it may choose to	fetch it.  If the
       implementation supports fetching	the cipher, then it may	use propquery
       as properties to	be queried for when fetching.  cipher_name may also be
       NULL, which will	result in unencrypted encoding.

       OSSL_ENCODER_CTX_set_passphrase() gives the implementation a pass
       phrase to use when encrypting the encoded private key.  Alternatively,
       a pass phrase callback may be specified with the	following functions.

       OSSL_ENCODER_CTX_set_passphrase_ui() and
       OSSL_ENCODER_CTX_set_passphrase_cb() sets up a callback method that the
       implementation can use to prompt	for a pass phrase, giving the caller
       the choice of prefered pass phrase callback form.  These	are called
       indirectly, through an internal OSSL_PASSPHRASE_CALLBACK	function.

   Output types
       The possible EVP_PKEY output types depends on the available

       OpenSSL has built in implementations for	the following output types:

	   The output is a human readable description of the key.
	   EVP_PKEY_print_private(3), EVP_PKEY_print_public(3) and
	   EVP_PKEY_print_params(3) use	this for their output.

	   The output is the DER encoding of the selection of the pkey.

	   The output is the selection of the pkey in PEM format.

       The following constants can be used for standard	selection:

	   Indicates that only the key parameters should be included in	the
	   output.  Where it matters, the data type in the output will
	   indicate that the data is parameters, not a key.

	   Indicates that the public key and eventual key parameters will be
	   included in the output.  Where it matters, the data type in the
	   output will indicate	that the data is a public key.

	   Indicates that the private key, the public key and eventual key
	   parameters should be	included in the	output.	 Where it matters, the
	   data	type in	the output will	indicate that the data is a private

       These are only indications, the encoder implementations are free	to
       determine what makes sense to include in	the output, and	this may
       depend on the desired output.  For example, an EC key in	a PKCS#8
       structure doesn't usually include the public key.

       OSSL_ENCODER_CTX_new_for_pkey() returns a pointer to an
       OSSL_ENCODER_CTX, or NULL if it couldn't	be created.

       OSSL_ENCODER_CTX_set_cipher(), OSSL_ENCODER_CTX_set_passphrase(),
       OSSL_ENCODER_CTX_set_passphrase_ui() and
       OSSL_ENCODER_CTX_set_passphrase_cb() all	return 1 on success, or	0 on

       provider(7), OSSL_ENCODER(3), OSSL_ENCODER_CTX(3)

       The functions described here were added in OpenSSL 3.0.

       Copyright 2019-2021 The OpenSSL Project Authors.	All Rights Reserved.

       Licensed	under the Apache License 2.0 (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

3.0.0-alpha12			  2021-02-18  OSSL_ENCODER_CTX_NEW_FOR_PKEY(3)


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