RSA_check_key(3)

     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.