NAME¶
EVP_PKEY_keygen_init, EVP_PKEY_keygen, EVP_PKEY_paramgen_init,
EVP_PKEY_paramgen, EVP_PKEY_CTX_set_cb, EVP_PKEY_CTX_get_cb,
EVP_PKEY_CTX_get_keygen_info, EVP_PKEVP_PKEY_CTX_set_app_data,
EVP_PKEY_CTX_get_app_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);
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 *data);
void *EVP_PKEY_CTX_get_app_data(EVP_PKEY_CTX *ctx);
DESCRIPTION¶
The
EVP_PKEY_keygen_init() function initializes a public key algorithm
context using key
pkey for a key genration 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 function
EVP_PKEY_set_cb() sets the key or parameter generation
callback to
cb. The function
EVP_PKEY_CTX_get_cb() returns the
key or parameter generation callback.
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_gen_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 genration 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".
NOTES¶
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 specifiic 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.
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;
/* Assumed param is set up already */
ctx = EVP_PKEY_CTX_new(param);
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_encrypt(3),
EVP_PKEY_decrypt(3),
EVP_PKEY_sign(3),
EVP_PKEY_verify(3),
EVP_PKEY_verify_recover(3),
EVP_PKEY_derive(3)
HISTORY¶
These functions were first added to OpenSSL 1.0.0.