Receive ascii string and return decrypted data.

        Avaiable digests:
            hex: Hexadecimal
            base64: Base 64
            hqx: hexbin4

def decrypt_ascii(self, ascii_string, key=None, digest="hex"):
        """
        Receive ascii string and return decrypted data.

        Avaiable digests:
            hex: Hexadecimal
            base64: Base 64
            hqx: hexbin4
        """
        digests = {"hex": binascii.a2b_hex,
                   "base64": binascii.a2b_base64,
                   "hqx": binascii.a2b_hqx}
        digestor = digests.get(digest)
        if not digestor:
            TripleSecError(u"Digestor not supported.")

        binary_string = digestor(ascii_string)
        result = self.decrypt(binary_string, key)
        return result