1DSA_set_method(3) OpenSSL DSA_set_method(3)
2
6 DSA_set_default_method, DSA_get_default_method, DSA_set_method,
7 DSA_new_method, DSA_OpenSSL - select DSA method
8
10 #include <openssl/dsa.h>
11 #include <openssl/engine.h>
12 void DSA_set_default_method(const DSA_METHOD *meth);
14 const DSA_METHOD *DSA_get_default_method(void);
16 int DSA_set_method(DSA *dsa, const DSA_METHOD *meth);
18 DSA *DSA_new_method(ENGINE *engine);
20 DSA_METHOD *DSA_OpenSSL(void);
22
24 A DSA_METHOD specifies the functions that OpenSSL uses for DSA
25 operations. By modifying the method, alternative implementations such
26 as hardware accelerators may be used. IMPORTANT: See the NOTES section
27 for important information about how these DSA API functions are
28 affected by the use of ENGINE API calls.
29 Initially, the default DSA_METHOD is the OpenSSL internal
31 implementation, as returned by DSA_OpenSSL().
32 DSA_set_default_method() makes meth the default method for all DSA
34 structures created later. NB: This is true only whilst no ENGINE has
35 been set as a default for DSA, so this function is no longer
36 recommended.
37 DSA_get_default_method() returns a pointer to the current default
39 DSA_METHOD. However, the meaningfulness of this result is dependent on
40 whether the ENGINE API is being used, so this function is no longer
41 recommended.
42 DSA_set_method() selects meth to perform all operations using the key
44 rsa. This will replace the DSA_METHOD used by the DSA key and if the
45 previous method was supplied by an ENGINE, the handle to that ENGINE
46 will be released during the change. It is possible to have DSA keys
47 that only work with certain DSA_METHOD implementations (eg. from an
48 ENGINE module that supports embedded hardware-protected keys), and in
49 such cases attempting to change the DSA_METHOD for the key can have
50 unexpected results.
51 DSA_new_method() allocates and initializes a DSA structure so that
53 engine will be used for the DSA operations. If engine is NULL, the
54 default engine for DSA operations is used, and if no default ENGINE is
55 set, the DSA_METHOD controlled by DSA_set_default_method() is used.
56
58 struct
59 {
60 /* name of the implementation */
61 const char *name;
62 /* sign */
64 DSA_SIG *(*dsa_do_sign)(const unsigned char *dgst, int dlen,
65 DSA *dsa);
66 /* pre-compute k^-1 and r */
68 int (*dsa_sign_setup)(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
69 BIGNUM **rp);
70 /* verify */
72 int (*dsa_do_verify)(const unsigned char *dgst, int dgst_len,
73 DSA_SIG *sig, DSA *dsa);
74 /* compute rr = a1^p1 * a2^p2 mod m (May be NULL for some
76 implementations) */
77 int (*dsa_mod_exp)(DSA *dsa, BIGNUM *rr, BIGNUM *a1, BIGNUM *p1,
78 BIGNUM *a2, BIGNUM *p2, BIGNUM *m,
79 BN_CTX *ctx, BN_MONT_CTX *in_mont);
80 /* compute r = a ^ p mod m (May be NULL for some implementations) */
82 int (*bn_mod_exp)(DSA *dsa, BIGNUM *r, BIGNUM *a,
83 const BIGNUM *p, const BIGNUM *m,
84 BN_CTX *ctx, BN_MONT_CTX *m_ctx);
85 /* called at DSA_new */
87 int (*init)(DSA *DSA);
88 /* called at DSA_free */
90 int (*finish)(DSA *DSA);
91 int flags;
93 char *app_data; /* ?? */
95 } DSA_METHOD;
97
99 DSA_OpenSSL() and DSA_get_default_method() return pointers to the
100 respective DSA_METHODs.
101 DSA_set_default_method() returns no value.
103 DSA_set_method() returns non-zero if the provided meth was successfully
105 set as the method for dsa (including unloading the ENGINE handle if the
106 previous method was supplied by an ENGINE).
107 DSA_new_method() returns NULL and sets an error code that can be
109 obtained by ERR_get_error(3) if the allocation fails. Otherwise it
110 returns a pointer to the newly allocated structure.
111
113 As of version 0.9.7, DSA_METHOD implementations are grouped together
114 with other algorithmic APIs (eg. RSA_METHOD, EVP_CIPHER, etc) in ENGINE
115 modules. If a default ENGINE is specified for DSA functionality using
116 an ENGINE API function, that will override any DSA defaults set using
117 the DSA API (ie. DSA_set_default_method()). For this reason, the
118 ENGINE API is the recommended way to control default implementations
119 for use in DSA and other cryptographic algorithms.
120
122 dsa(3), DSA_new(3)
123
125 DSA_set_default_method(), DSA_get_default_method(), DSA_set_method(),
126 DSA_new_method() and DSA_OpenSSL() were added in OpenSSL 0.9.4.
127 DSA_set_default_openssl_method() and DSA_get_default_openssl_method()
129 replaced DSA_set_default_method() and DSA_get_default_method()
130 respectively, and DSA_set_method() and DSA_new_method() were altered to
131 use ENGINEs rather than DSA_METHODs during development of the engine
132 version of OpenSSL 0.9.6. For 0.9.7, the handling of defaults in the
133 ENGINE API was restructured so that this change was reversed, and
134 behaviour of the other functions resembled more closely the previous
135 behaviour. The behaviour of defaults in the ENGINE API now
136 transparently overrides the behaviour of defaults in the DSA API
137 without requiring changing these function prototypes.
1381.0.1e 2013-02-11 DSA_set_method(3)