## NAME

`RSA_set_default_method`

,
`RSA_get_default_method`

,
`RSA_set_method`

,
`RSA_get_method`

,
`RSA_PKCS1_SSLeay`

, `RSA_flags`

,
`RSA_new_method`

—
select RSA method

## SYNOPSIS

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

`void`

`RSA_set_default_method`

(`const
RSA_METHOD *meth`);

`const RSA_METHOD *`

`RSA_get_default_method`

(`void`);

`int`

`RSA_set_method`

(`RSA *rsa`,
`const RSA_METHOD *meth`);

`const RSA_METHOD *`

`RSA_get_method`

(`const RSA
*rsa`);

`const RSA_METHOD *`

`RSA_PKCS1_SSLeay`

(`void`);

`int`

`RSA_flags`

(`const RSA *rsa`);

`RSA *`

`RSA_new_method`

(`ENGINE
*engine`);

## DESCRIPTION

An `RSA_METHOD` object contains pointers to
the functions used for RSA operations. By default, the internal
implementation returned by
`RSA_PKCS1_SSLeay`

()
is used. By selecting another method, alternative implementations such as
hardware accelerators may be used.

`RSA_set_default_method`

()
selects `meth` as 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` to perform all operations using the key
`rsa`. This replaces the previous
`RSA_METHOD` used by the RSA key, calling the
`finish` function set up with
RSA_meth_set_finish(3) if any. If `meth`
contains an `init` function set up with
RSA_meth_set_init(3), that function is called just before
returning from `RSA_set_method`

().

It is possible to have RSA keys that only work with certain
`RSA_METHOD` implementations, and in such cases
attempting to change the `RSA_METHOD` for the key can
have unexpected results.

`RSA_get_method`

()
returns a pointer to the `RSA_METHOD` being used by
`rsa`.

The misleadingly named function
`RSA_flags`

()
returns the flags that are set for the current
`RSA_METHOD` of `rsa`. The flags
used by `rsa` itself can instead be tested with
RSA_test_flags(3). See the BUGS
section for more details.

`RSA_new_method`

()
allocates and initializes an `RSA` structure. The
`engine` argument is ignored and the default method
controlled by `RSA_set_default_method`

() is used.

The initial `flags` are
copied from the `RSA_METHOD` object used and will not be
affected by later changes to that object, but may be modified by the
optional `init` function which may have been set up with
RSA_meth_set_init(3) and which is called just before
returning from
`RSA_new_method`

().

## RETURN VALUES

`RSA_PKCS1_SSLeay`

(),
`RSA_get_default_method`

(), and
`RSA_get_method`

() return pointers to the respective
`RSA_METHOD`.

`RSA_set_method`

() returns 1 on success or 0
on failure. Currently, it cannot fail.

`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

## HISTORY

`RSA_set_default_method`

(),
`RSA_PKCS1_SSLeay`

(), and
`RSA_new_method`

() first appeared in SSLeay 0.8.0.
`RSA_flags`

() first appeared in SSLeay 0.9.0. These
functions have been available since OpenBSD 2.4.

`RSA_get_default_method`

(),
`RSA_set_method`

(), and
`RSA_get_method`

() as well as the
`rsa_sign` and `rsa_verify`
components of `RSA_METHOD` first appeared in OpenSSL
0.9.4 and have been available since OpenBSD 2.6.

## BUGS

The behaviour of `RSA_flags`

() is a
misfeature that is left as-is for now to avoid creating compatibility
problems. RSA functionality, such as the encryption functions, are
controlled by the `flags` value in the
`RSA` key itself, not by the `flags`
value in the `RSA_METHOD` attached to the RSA key (which
is what this function returns). If the flags element of an
`RSA` key is changed, the changes will be honoured by
RSA functionality but will not be reflected in the return value of the
`RSA_flags`

() function - in effect
`RSA_flags`

() behaves more like an
`RSA_default_flags`

() function, which does not
currently exist.