RSA_set_method(3)

NAME
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>

 void RSA_set_default_method(RSA_METHOD *meth);

 RSA_METHOD *RSA_get_default_method(void);

 RSA_METHOD *RSA_set_method(RSA *rsa, RSA_METHOD *meth);

 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(RSA_METHOD *method);

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_method() makes meth the default method for all RSA structures created later.

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

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

RSA_get_method() returns a pointer to the method currently selected 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 method will be used for the RSA operations. If method is NULL, the default method 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);

     /* RSA_FLAG_EXT_PKEY        - rsa_mod_exp is called for private key
      *                            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_method() and RSA_get_method() return pointers to the respective RSA_METHODs.

RSA_set_default_method() returns no value.

RSA_set_method() returns a pointer to the RSA_METHOD previously associated with 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 rsa_verify components of RSA_METHOD were added in OpenSSL 0.9.4.