The invention allows SMS messages authentication through the use of a digital signature computed with the International Mobile Equipment Identity (IMEI) as a key. Particularly, a text messaging system having the ability to send SMS messages to remotely managed wireless terminal equipment is disclosed and includes a system to generate such digital signature and to store it in available Information Element fields of the TP-User Data of the SMS message. Receiving wireless terminal equipment that are configured for IMEI-based signature security, still keep the option to process both SMS messages having the IMEI-based signature or not. Receiving wireless terminal equipment not enabled for IMEI-based signature security process the SMS normally.