def crypto_revision_from_options(params)
            case params[:cipher].upcase
            when 'RC4'
                crypto_revision_from_rc4_key(params[:key_size])
            when 'AES'
                crypto_revision_from_aes_key(params[:key_size], params[:hardened])
            else
                raise EncryptionNotSupportedError, "Cipher not supported : #{params[:cipher]}"
            end
        end
def crypto_revision_from_options(params)
            case params[:cipher].upcase
            when 'RC4'
                crypto_revision_from_rc4_key(params[:key_size])
            when 'AES'
                crypto_revision_from_aes_key(params[:key_size], params[:hardened])
            else
                raise EncryptionNotSupportedError, "Cipher not supported : #{params[:cipher]}"
            end
        end
Converts the parameters passed to PDF#encrypt.
 Returns [ version, revision, crypt_filters ]