DSA_SET_METHOD(3) | Library Functions Manual | DSA_SET_METHOD(3)

# NAME

`DSA_set_default_method`, `DSA_get_default_method`, `DSA_set_method`, `DSA_new_method`, `DSA_OpenSSL` — select DSA method

# SYNOPSIS

library “libcrypto”
`#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.

June 8, 2025 | Debian