gen key

if(CryptGetUserKey(
            hCryptProv,
            AT_KEYEXCHANGE,
            &hXchgKey))
        {
            _tprintf(
                TEXT("The user public key has been retrieved. \n"));
        }
        else
        {
            if(NTE_NO_KEY == GetLastError())
            {
                // No exchange key exists. Try to create one.
                if(!CryptGenKey(
                    hCryptProv,
                    AT_KEYEXCHANGE,
                    CRYPT_EXPORTABLE,
                    &hXchgKey))
                {
                    MyHandleError(
                        TEXT("Could not create "
                            "a user public key.\n"),
                        GetLastError());
                    goto Exit_MyEncryptFile;
                }
            }
            else
            {
                MyHandleError(
                    TEXT("User public key is not available and may ")
                        TEXT("not exist.\n"),
                    GetLastError());
                goto Exit_MyEncryptFile;
            }
        }