Keygen docs.

doc/crypto/EVP_PKEY_keygen.pod

+=pod
+
+=head1 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
+
+=head1 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);
+
+=head1 DESCRIPTION
+
+The EVP_PKEY_keygen_init() function initializes a public key algorithm
+context using key B<pkey> for a key genration operation.
+
+The EVP_PKEY_keygen() function performs a key generation operation, the 
+generated key is written to B<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 B<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 B<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
+B<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".
+
+=head1 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.
+
+=head1 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.
+
+=head1 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;
+	}
+
+=head1 SEE ALSO
+
+L<EVP_PKEY_CTX_new(3)|EVP_PKEY_CTX_new(3)>,
+L<EVP_PKEY_encrypt(3)|EVP_PKEY_encrypt(3)>,
+L<EVP_PKEY_decrypt(3)|EVP_PKEY_decrypt(3)>,
+L<EVP_PKEY_sign(3)|EVP_PKEY_sign(3)>,
+L<EVP_PKEY_verify(3)|EVP_PKEY_verify(3)>,
+L<EVP_PKEY_verifyrecover(3)|EVP_PKEY_verifyrecover(3)>,
+L<EVP_PKEY_derive(3)|EVP_PKEY_derive(3)> 
+
+=head1 HISTORY
+
+These functions were first added to OpenSSL 0.9.9.
+
+=cut