RSA_set_default_method, RSA_get_default_method,
       RSA_set_method, RSA_get_method, RSA_PKCS1_SSLeay,
       RSA_PKCS1_RSAref, RSA_null_method, RSA_flags,
       RSA_new_method - select RSA method


SYNOPSIS

        #include <openssl/rsa.h>
        #include <openssl/engine.h>

        void RSA_set_default_openssl_method(RSA_METHOD *meth);

        RSA_METHOD *RSA_get_default_openssl_method(void);

        RSA_METHOD *RSA_set_method(RSA *rsa, ENGINE *engine);

        RSA_METHOD *RSA_get_method(RSA *rsa);

        RSA_METHOD *RSA_PKCS1_SSLeay(void);

        RSA_METHOD *RSA_PKCS1_RSAref(void);

        RSA_METHOD *RSA_null_method(void);

        int RSA_flags(RSA *rsa);

        RSA *RSA_new_method(ENGINE *engine);


DESCRIPTION

       An RSA_METHOD specifies the functions that OpenSSL uses
       for RSA operations. By modifying the method, alternative
       implementations such as hardware accelerators may be used.

       Initially, the default is to use the OpenSSL internal
       implementation, unless OpenSSL was configured with the
       rsaref or -DRSA_NULL options. RSA_PKCS1_SSLeay() returns a
       pointer to that method.

       RSA_PKCS1_RSAref() returns a pointer to a method that uses
       the RSAref library. This is the default method in the
       rsaref configuration; the function is not available in
       other configurations.  RSA_null_method() returns a pointer
       to a method that does not support the RSA transformation.
       It is the default if OpenSSL is compiled with -DRSA_NULL.
       These methods may be useful in the USA because of a patent
       on the RSA cryptosystem.

       RSA_set_default_openssl_method() makes meth the default
       method for all RSA structures created later. NB: This is
       true only whilst the default engine for RSA operations
       remains as "openssl". ENGINEs provide an encapsulation for
       implementations of one or more algorithms at a time, and
       all the RSA functions mentioned here operate within the


       RSA_get_default_openssl_method() returns a pointer to the
       current default method for the "openssl" engine.

       RSA_set_method() selects engine for all operations using
       the key rsa.

       RSA_get_method() returns a pointer to the RSA_METHOD from
       the currently selected ENGINE for rsa.

       RSA_flags() returns the flags that are set for rsa's
       current method.

       RSA_new_method() allocates and initializes an RSA
       structure so that engine will be used for the RSA
       operations. If engine is NULL, the default engine for RSA
       operations is used.


THE RSA_METHOD STRUCTURE

        typedef struct rsa_meth_st
        {
            /* name of the implementation */
               const char *name;

            /* encrypt */
               int (*rsa_pub_enc)(int flen, unsigned char *from,
                 unsigned char *to, RSA *rsa, int padding);

            /* verify arbitrary data */
               int (*rsa_pub_dec)(int flen, unsigned char *from,
                 unsigned char *to, RSA *rsa, int padding);

            /* sign arbitrary data */
               int (*rsa_priv_enc)(int flen, unsigned char *from,
                 unsigned char *to, RSA *rsa, int padding);

            /* decrypt */
               int (*rsa_priv_dec)(int flen, unsigned char *from,
                 unsigned char *to, RSA *rsa, int padding);

            /* compute r0 = r0 ^ I mod rsa->n (May be NULL for some
                                               implementations) */
               int (*rsa_mod_exp)(BIGNUM *r0, BIGNUM *I, RSA *rsa);

            /* compute r = a ^ p mod m (May be NULL for some implementations) */
               int (*bn_mod_exp)(BIGNUM *r, BIGNUM *a, const BIGNUM *p,
                 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);

            /* called at RSA_new */
               int (*init)(RSA *rsa);

            /* called at RSA_free */
               int (*finish)(RSA *rsa);

             *                            operations, even if p,q,dmp1,dmq1,iqmp
             *                            are NULL
             * RSA_FLAG_SIGN_VER        - enable rsa_sign and rsa_verify
             * RSA_METHOD_FLAG_NO_CHECK - don't check pub/private match
             */
               int flags;

               char *app_data; /* ?? */

            /* sign. For backward compatibility, this is used only
             * if (flags & RSA_FLAG_SIGN_VER)
             */
               int (*rsa_sign)(int type, unsigned char *m, unsigned int m_len,
                  unsigned char *sigret, unsigned int *siglen, RSA *rsa);

            /* verify. For backward compatibility, this is used only
             * if (flags & RSA_FLAG_SIGN_VER)
             */
               int (*rsa_verify)(int type, unsigned char *m, unsigned int m_len,
                  unsigned char *sigbuf, unsigned int siglen, RSA *rsa);

        } RSA_METHOD;


RETURN VALUES

       RSA_PKCS1_SSLeay(), RSA_PKCS1_RSAref(),
       RSA_PKCS1_null_method(), RSA_get_default_openssl_method()
       and RSA_get_method() return pointers to the respective
       RSA_METHODs.

       RSA_set_default_openssl_method() returns no value.

       RSA_set_method() selects engine as the engine that will be
       responsible for all operations using the structure rsa. If
       this function completes successfully, then the rsa
       structure will have its own functional reference of
       engine, so the caller should remember to free their own
       reference to engine when they are finished with it. NB: An
       ENGINE's RSA_METHOD can be retrieved (or set) by
       ENGINE_get_RSA() or ENGINE_set_RSA().

       RSA_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

       rsa(3), RSA_new(3)


HISTORY

       RSA_new_method() and RSA_set_default_method() appeared in
       SSLeay 0.8.  RSA_get_default_method(), RSA_set_method()
       and RSA_get_method() as well as the rsa_sign and

       0.9.4.

       RSA_set_default_openssl_method() and
       RSA_get_default_openssl_method() replaced
       RSA_set_default_method() and RSA_get_default_method()
       respectively, and RSA_set_method() and RSA_new_method()
       were altered to use ENGINEs rather than DH_METHODs during
       development of OpenSSL 0.9.6.

       RSA_null_method, RSA_flags, RSA_new_method - select RSA
       method"


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