Reference

libressl-DSA_set_method(3)

select DSA method

NAME

DSA_set_default_method, DSA_get_default_method, DSA_set_method, DSA_new_method, DSA_OpenSSL – select DSA method

SYNOPSIS

Crypto Library (libcrypto, -lcrypto)

#include <openssl/dsa.h>

void

DSA_set_default_method(const DSA_METHOD *meth);

const DSA_METHOD *

DSA_get_default_method(void);

int

DSA_set_method(DSA *dsa, const DSA_METHOD *meth);

DSA *

DSA_new_method(ENGINE *engine);

DSA_METHOD *

DSA_OpenSSL(void);

DESCRIPTION

A DSA_METHOD object contains pointers to the functions used for DSA operations. By default, the internal implementation returned by DSA_OpenSSL() is used. By selecting another method, alternative implementations such as hardware accelerators may be used.

DSA_set_default_method() selects meth as the default method for all DSA structures created later.

DSA_get_default_method() returns a pointer to the current default method.

DSA_set_method() selects meth to perform all operations using the key dsa. This replaces the DSA_METHOD used by the DSA key. It is possible to have DSA keys that only work with certain DSA_METHOD implementations, and in such cases attempting to change the DSA_METHOD for the key can have unexpected results.

DSA_new_method() allocates and initializes a DSA structure. The engine argument is ignored and the default method controlled by DSA_set_default_method() is used.

The DSA_METHOD structure is defined as follows:

struct {
	/* name of the implementation */
	const char *name;
	/* sign */
	DSA_SIG *(*dsa_do_sign)(const unsigned char *dgst, int dlen,
	    DSA *dsa);
	/* pre-compute k^-1 and r */
	int (*dsa_sign_setup)(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
	    BIGNUM **rp);
	/* verify */
	int (*dsa_do_verify)(const unsigned char *dgst, int dgst_len,
	    DSA_SIG *sig, DSA *dsa);
	/* called at DSA_new */
	int (*init)(DSA *DSA);
	/* called at DSA_free */
	int (*finish)(DSA *DSA);
	int flags;
} DSA_METHOD;

RETURN VALUES

DSA_OpenSSL() and DSA_get_default_method() return pointers to the respective DSA_METHOD.

DSA_set_method() returns 1 on success or 0 on failure. Currently, it cannot fail.

DSA_new_method() returns NULL and sets an error code that can be obtained by ERR_get_error(3) if the allocation fails. Otherwise it returns a pointer to the newly allocated structure.

SEE ALSO

DSA_meth_new(3), DSA_new(3)

HISTORY

DSA_set_default_method(), DSA_get_default_method(), DSA_set_method(), DSA_new_method(), and DSA_OpenSSL() first appeared in OpenSSL 0.9.5 and have been available since OpenBSD 2.7.