Patent ID: 7296156

Claim:
A text messaging system for encryption of a text message sent to a wireless terminal equipment, the text message comprising a Short Message Service (SMS) message having a User Data Header (UDH) and a text data field, the text messaging system comprising: means for storing an equipment identification number uniquely assigned to the wireless terminal equipment, wherein the assigned equipment identification number is an International Mobile Equipment Identity (IMEI) number of the wireless terminal equipment; means coupled to the equipment identification number storing means for encrypting the text data field content of the SMS message using only the IMEI number assigned to the wireless terminal equipment as the shared key; and means for setting an encryption identifier in an Information Element (IE) group of the UDH of the SMS message, the encryption identifier comprising a marker in an IE data field, the IE group further comprising an Information Element Identifier (IEI) field set to indicate a presence of the marker, and an Information Element Data Length (IEDL) field set to indicate a length of the marker.