<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def decrypt_assertions(self, encrypted_assertions, decr_txt, issuer=None, verified=False):
 """ Moves the decrypted assertion from the encrypted assertion to a list. :param encrypted_assertions: A list of encrypted assertions. :param decr_txt: The string representation containing the decrypted data. Used when verifying signatures. :param issuer: The issuer of the response. :param verified: If True do not verify signatures, otherwise verify the signature if it exists. :return: A list of decrypted assertions. """

        res = []
        for encrypted_assertion in encrypted_assertions:
            if encrypted_assertion.extension_elements:
                assertions = extension_elements_to_elements(
                    encrypted_assertion.extension_elements, [saml, samlp])
                for assertion in assertions:
                    if assertion.signature and not verified:
                        if not self.sec.check_signature(
                                assertion, origdoc=decr_txt,
                                node_name=class_name(assertion), issuer=issuer):
                            logger.error("Failed to verify signature on '%s'",
                                         assertion)
                            raise SignatureError()
                    res.append(assertion)
        return res