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Diffstat (limited to 'openssl/doc/crypto/DSA_set_method.pod')
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diff --git a/openssl/doc/crypto/DSA_set_method.pod b/openssl/doc/crypto/DSA_set_method.pod new file mode 100644 index 000000000..9c1434bd8 --- /dev/null +++ b/openssl/doc/crypto/DSA_set_method.pod @@ -0,0 +1,143 @@ +=pod + +=head1 NAME + +DSA_set_default_method, DSA_get_default_method, +DSA_set_method, DSA_new_method, DSA_OpenSSL - select DSA method + +=head1 SYNOPSIS + + #include <openssl/dsa.h> + #include <openssl/engine.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); + +=head1 DESCRIPTION + +A B<DSA_METHOD> specifies the functions that OpenSSL uses for DSA +operations. By modifying the method, alternative implementations +such as hardware accelerators may be used. IMPORTANT: See the NOTES section for +important information about how these DSA API functions are affected by the use +of B<ENGINE> API calls. + +Initially, the default DSA_METHOD is the OpenSSL internal implementation, +as returned by DSA_OpenSSL(). + +DSA_set_default_method() makes B<meth> the default method for all DSA +structures created later. B<NB>: This is true only whilst no ENGINE has +been set as a default for DSA, so this function is no longer recommended. + +DSA_get_default_method() returns a pointer to the current default +DSA_METHOD. However, the meaningfulness of this result is dependent on +whether the ENGINE API is being used, so this function is no longer +recommended. + +DSA_set_method() selects B<meth> to perform all operations using the key +B<rsa>. This will replace the DSA_METHOD used by the DSA key and if the +previous method was supplied by an ENGINE, the handle to that ENGINE will +be released during the change. It is possible to have DSA keys that only +work with certain DSA_METHOD implementations (eg. from an ENGINE module +that supports embedded hardware-protected keys), 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 so that B<engine> +will be used for the DSA operations. If B<engine> is NULL, the default engine +for DSA operations is used, and if no default ENGINE is set, the DSA_METHOD +controlled by DSA_set_default_method() is used. + +=head1 THE DSA_METHOD STRUCTURE + +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); + + /* compute rr = a1^p1 * a2^p2 mod m (May be NULL for some + implementations) */ + int (*dsa_mod_exp)(DSA *dsa, BIGNUM *rr, BIGNUM *a1, BIGNUM *p1, + BIGNUM *a2, BIGNUM *p2, BIGNUM *m, + BN_CTX *ctx, BN_MONT_CTX *in_mont); + + /* compute r = a ^ p mod m (May be NULL for some implementations) */ + int (*bn_mod_exp)(DSA *dsa, BIGNUM *r, BIGNUM *a, + const BIGNUM *p, const BIGNUM *m, + BN_CTX *ctx, BN_MONT_CTX *m_ctx); + + /* called at DSA_new */ + int (*init)(DSA *DSA); + + /* called at DSA_free */ + int (*finish)(DSA *DSA); + + int flags; + + char *app_data; /* ?? */ + + } DSA_METHOD; + +=head1 RETURN VALUES + +DSA_OpenSSL() and DSA_get_default_method() return pointers to the respective +B<DSA_METHOD>s. + +DSA_set_default_method() returns no value. + +DSA_set_method() returns non-zero if the provided B<meth> was successfully set as +the method for B<dsa> (including unloading the ENGINE handle if the previous +method was supplied by an ENGINE). + +DSA_new_method() returns NULL and sets an error code that can be +obtained by L<ERR_get_error(3)|ERR_get_error(3)> if the allocation +fails. Otherwise it returns a pointer to the newly allocated structure. + +=head1 NOTES + +As of version 0.9.7, DSA_METHOD implementations are grouped together with other +algorithmic APIs (eg. RSA_METHOD, EVP_CIPHER, etc) in B<ENGINE> modules. If a +default ENGINE is specified for DSA functionality using an ENGINE API function, +that will override any DSA defaults set using the DSA API (ie. +DSA_set_default_method()). For this reason, the ENGINE API is the recommended way +to control default implementations for use in DSA and other cryptographic +algorithms. + +=head1 SEE ALSO + +L<dsa(3)|dsa(3)>, L<DSA_new(3)|DSA_new(3)> + +=head1 HISTORY + +DSA_set_default_method(), DSA_get_default_method(), DSA_set_method(), +DSA_new_method() and DSA_OpenSSL() were added in OpenSSL 0.9.4. + +DSA_set_default_openssl_method() and DSA_get_default_openssl_method() replaced +DSA_set_default_method() and DSA_get_default_method() respectively, and +DSA_set_method() and DSA_new_method() were altered to use B<ENGINE>s rather than +B<DSA_METHOD>s during development of the engine version of OpenSSL 0.9.6. For +0.9.7, the handling of defaults in the ENGINE API was restructured so that this +change was reversed, and behaviour of the other functions resembled more closely +the previous behaviour. The behaviour of defaults in the ENGINE API now +transparently overrides the behaviour of defaults in the DSA API without +requiring changing these function prototypes. + +=cut |