The disclosed invention allows security of configuration SMS messages through the use of encryption 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 comprises means to generate an encrypted bit string based on the IMEI shared key and to signal use of the security mechanism in available Information Element fields of the TP-User Data of the SMS message. The receiving wireless terminal equipment is configured to process configuration SMS messages encrypted using the IMEI as a key.