NAME
EVP_PKEY_keygen_init
,
EVP_PKEY_keygen
,
EVP_PKEY_paramgen_init
,
EVP_PKEY_paramgen
,
EVP_PKEY_gen_cb
,
EVP_PKEY_CTX_set_cb
,
EVP_PKEY_CTX_get_cb
,
EVP_PKEY_CTX_set0_keygen_info
,
EVP_PKEY_CTX_get_keygen_info
,
EVP_PKEY_CTX_set_app_data
,
EVP_PKEY_CTX_get_app_data
,
EVP_PKEY_CTX_set_data
,
EVP_PKEY_CTX_get_data
—
key and parameter generation
functions
SYNOPSIS
#include
<openssl/evp.h>
int
EVP_PKEY_keygen_init
(EVP_PKEY_CTX
*ctx);
int
EVP_PKEY_keygen
(EVP_PKEY_CTX
*ctx, EVP_PKEY **ppkey);
int
EVP_PKEY_paramgen_init
(EVP_PKEY_CTX
*ctx);
int
EVP_PKEY_paramgen
(EVP_PKEY_CTX
*ctx, EVP_PKEY **ppkey);
typedef int
EVP_PKEY_gen_cb
(EVP_PKEY_CTX
*ctx);
void
EVP_PKEY_CTX_set_cb
(EVP_PKEY_CTX
*ctx, EVP_PKEY_gen_cb *cb);
EVP_PKEY_gen_cb *
EVP_PKEY_CTX_get_cb
(EVP_PKEY_CTX
*ctx);
void
EVP_PKEY_CTX_set0_keygen_info
(EVP_PKEY_CTX
*ctx, int *dat, int
datlen);
int
EVP_PKEY_CTX_get_keygen_info
(EVP_PKEY_CTX
*ctx, int idx);
void
EVP_PKEY_CTX_set_app_data
(EVP_PKEY_CTX
*ctx, void *app_data);
void *
EVP_PKEY_CTX_get_app_data
(EVP_PKEY_CTX
*ctx);
void
EVP_PKEY_CTX_set_data
(EVP_PKEY_CTX
*ctx, void *data);
void *
EVP_PKEY_CTX_get_data
(EVP_PKEY_CTX
*ctx);
DESCRIPTION
The
EVP_PKEY_keygen_init
()
function initializes a public key algorithm context using key
ctx->pkey for a key generation operation.
The
EVP_PKEY_keygen
()
function performs a key generation operation. The generated key is written
to ppkey.
The functions
EVP_PKEY_paramgen_init
()
and
EVP_PKEY_paramgen
()
are similar except parameters are generated.
The functions
EVP_PKEY_CTX_set_cb
()
and
EVP_PKEY_CTX_get_cb
()
set and retrieve the key or parameter generation callback, respectively.
The function
EVP_PKEY_CTX_set0_keygen_info
()
sets the parameters associated with the generation operation to the array
dat containing datlen integer
parameters. The caller retains ownership of the dat
array; it will never be freed by the library.
The function
EVP_PKEY_CTX_get_keygen_info
()
returns parameters associated with the generation operation. If
idx is -1, the total number of parameters available is
returned. Any non-negative value returns the value of that parameter.
EVP_PKEY_CTX_get_keygen_info
() with a non-negative
value for idx should only be called within the
generation callback.
If the callback returns 0, then the key generation operation is aborted and an error occurs. This might occur during a time consuming operation where a user clicks on a "cancel" button.
The functions
EVP_PKEY_CTX_set_app_data
()
and
EVP_PKEY_CTX_get_app_data
()
set and retrieve an opaque pointer. This can be used to set some application
defined value which can be retrieved in the callback: for example a handle
which is used to update a "progress dialog".
The deprecated functions
EVP_PKEY_CTX_set_data
()
and
EVP_PKEY_CTX_get_data
()
set and retrieve a
different
opaque pointer that is ignored by the library.
After the call to
EVP_PKEY_keygen_init
()
or EVP_PKEY_paramgen_init
(), algorithm specific
control operations can be performed to set any appropriate parameters for
the operation.
The functions
EVP_PKEY_keygen
()
and
EVP_PKEY_paramgen
()
can be called more than once on the same context if several operations are
performed using the same parameters.
The meaning of the parameters passed to the callback will depend on the algorithm and the specific implementation of the algorithm. Some might not give any useful information at all during key or parameter generation. Others might not even call the callback.
The operation performed by key or parameter generation depends on the algorithm used. In some cases (e.g. EC with a supplied named curve) the "generation" option merely sets the appropriate fields in an EVP_PKEY structure.
In OpenSSL, an EVP_PKEY structure containing a private key also contains the public key components and parameters (if any). An OpenSSL private key is equivalent to what some libraries call a "key pair". A private key can be used in functions which require the use of a public key or parameters.
RETURN VALUES
EVP_PKEY_keygen_init
(),
EVP_PKEY_paramgen_init
(),
EVP_PKEY_keygen
(), and
EVP_PKEY_paramgen
() return 1 for success and 0 or a
negative value for failure. In particular, a return value of -2 indicates
the operation is not supported by the public key algorithm.
Callback functions of the type
EVP_PKEY_gen_cb
() are supposed to return 1 on
success or 0 on error.
EVP_PKEY_CTX_get_cb
() returns a function
pointer to the currently installed callback function or
NULL
if no callback function is installed.
EVP_PKEY_CTX_get_keygen_info
() returns the
number of available parameters if idx is -1, one of
these parameters if idx is greater than or equal to
zero but less than the number of available parameters, or 0 otherwise.
EVP_PKEY_CTX_get_app_data
() and
EVP_PKEY_CTX_get_data
() return the pointer that was
last passed to the corresponding set function, or
NULL
if the corresponding set function was never
called on ctx.
EXAMPLES
Generate a 2048-bit RSA key:
#include <openssl/evp.h> #include <openssl/rsa.h> EVP_PKEY_CTX *ctx; EVP_PKEY *pkey = NULL; ctx = EVP_PKEY_CTX_new_id(EVP_PKEY_RSA, NULL); if (!ctx) /* Error occurred */ if (EVP_PKEY_keygen_init(ctx) <= 0) /* Error */ if (EVP_PKEY_CTX_set_rsa_keygen_bits(ctx, 2048) <= 0) /* Error */ /* Generate key */ if (EVP_PKEY_keygen(ctx, &pkey) <= 0) /* Error */
Generate a key from a set of parameters:
#include <openssl/evp.h> #include <openssl/rsa.h> EVP_PKEY_CTX *ctx; EVP_PKEY *pkey = NULL, *param; /* Assumes that param is already set up. */ ctx = EVP_PKEY_CTX_new(param, NULL); if (!ctx) /* Error occurred */ if (EVP_PKEY_keygen_init(ctx) <= 0) /* Error */ /* Generate key */ if (EVP_PKEY_keygen(ctx, &pkey) <= 0) /* Error */
Example of generation callback for OpenSSL public key implementations:
/* Application data is a BIO to output status to */ EVP_PKEY_CTX_set_app_data(ctx, status_bio); static int genpkey_cb(EVP_PKEY_CTX *ctx) { char c = '*'; BIO *b = EVP_PKEY_CTX_get_app_data(ctx); int p; p = EVP_PKEY_CTX_get_keygen_info(ctx, 0); if (p == 0) c = '.'; if (p == 1) c = '+'; if (p == 2) c = '*'; if (p == 3) c = '\n'; BIO_write(b, &c, 1); (void)BIO_flush(b); return 1; }
SEE ALSO
EVP_PKEY_CTX_new(3), EVP_PKEY_decrypt(3), EVP_PKEY_derive(3), EVP_PKEY_encrypt(3), EVP_PKEY_sign(3), EVP_PKEY_verify(3), EVP_PKEY_verify_recover(3), X25519(3)
HISTORY
These functions first appeared in OpenSSL 1.0.0 and have been available since OpenBSD 4.9.