NAME

       RSA_check_key - validate private RSA keys

SYNOPSIS

        #include <openssl/rsa.h>

        int RSA_check_key(RSA *rsa);

DESCRIPTION

       This function validates RSA keys. It checks that p and q are in fact prime, and that n =
       p*q.

       It also checks that d*e = 1 mod (p-1*q-1), and that dmp1, dmq1 and iqmp are set correctly
       or are NULL.

       As such, this function can not be used with any arbitrary RSA key object, even if it is
       otherwise fit for regular RSA operation. See NOTES for more information.

RETURN VALUE

       RSA_check_key() returns 1 if rsa is a valid RSA key, and 0 otherwise.  -1 is returned if
       an error occurs while checking the key.

       If the key is invalid or an error occurred, the reason code can be obtained using
       ERR_get_error(3).

NOTES

       This function does not work on RSA public keys that have only the modulus and public
       exponent elements populated. It performs integrity checks on all the RSA key material, so
       the RSA key structure must contain all the private key data too.

       Unlike most other RSA functions, this function does not work transparently with any
       underlying ENGINE implementation because it uses the key data in the RSA structure
       directly. An ENGINE implementation can override the way key data is stored and handled,
       and can even provide support for HSM keys - in which case the RSA structure may contain no
       key data at all! If the ENGINE in question is only being used for acceleration or analysis
       purposes, then in all likelihood the RSA key data is complete and untouched, but this
       can't be assumed in the general case.

BUGS

       A method of verifying the RSA key using opaque RSA API functions might need to be
       considered. Right now RSA_check_key() simply uses the RSA structure elements directly,
       bypassing the RSA_METHOD table altogether (and completely violating encapsulation and
       object-orientation in the process).  The best fix will probably be to introduce a
       "check_key()" handler to the RSA_METHOD function table so that alternative implementations
       can also provide their own verifiers.

SEE ALSO

       rsa(3), ERR_get_error(3)

HISTORY

       RSA_check_key() appeared in OpenSSL 0.9.4.