def decrypt(self, passphrase: str) -> bytes:
        """
        Converts the Encrypted Master Secret to a Master Secret by applying the passphrase.
        This is analogous to BIP-39 passphrase derivation. We do not use the term "derive"
        here, because passphrase function is symmetric in SLIP-39. We are using the terms
        "encrypt" and "decrypt" instead.
        """
        passphrase = (passphrase or '').encode('utf-8')
        ems_len = len(self.encrypted_master_secret)
        l = self.encrypted_master_secret[: ems_len // 2]
        r = self.encrypted_master_secret[ems_len // 2 :]
        salt = _get_salt(self.identifier, self.extendable_backup_flag)
        for i in reversed(range(_ROUND_COUNT)):
            (l, r) = (
                r,
                _xor(l, _round_function(i, passphrase, self.iteration_exponent, salt, r)),
            )
        return r + l

        Converts the Encrypted Master Secret to a Master Secret by applying the passphrase.
        This is analogous to BIP-39 passphrase derivation. We do not use the term "derive"
        here, because passphrase function is symmetric in SLIP-39. We are using the terms
        "encrypt" and "decrypt" instead.
        
electrum/slip39.py