def get_common_session_key(self, premaster_secret):
k_1 = self.hash(premaster_secret, b'<STR_LIT>', as_bytes=True)<EOL>k_2 = self.hash(premaster_secret, b'<STR_LIT>', as_bytes=True)<EOL>return k_1 + k_2<EOL>
K = H(S).

        Special implementation for Apple TV.