To use UTF-8 as your encoding, use unicode.encode('utf-8')
to convert from a unicode string to a UTF-8 encoded string, and string.decode('utf-8')
to convert from a UTF-8 encoded string to a unicode string (yes, they are different):
secret = u'ककककक.'.encode('utf-8')
message = u'कककककककककककक'.encode('utf-8')
decoded = DecodeAES(obj, encoded).decode('utf-8')