<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def encrypt(self, msg):
 """encrypts a message"""

        iv = self.random_bytes(AES.block_size)
        ctr = Counter.new(AES.block_size * 8, initial_value=self.bin2long(iv))
        cipher = AES.AESCipher(self._cipherkey, AES.MODE_CTR, counter=ctr)
        cipher_text = cipher.encrypt(msg)
        intermediate = iv + cipher_text
        signature = self.sign(intermediate)
        return signature + intermediate