All e-commerce environments require support for security properties such as authentication, authorization, data confidentiality, and nonrepudiation. E-commerce protocols such as SSL, TLS, and SET offer security for e-transactions, but they are specific to the unicast (point-to-point) environment. They cannot be directly extended to provide security for multicast (point-to-multipoint) sessions. Multicast data transmission provides significant network resource savings for applications such as audio/video streaming, news broadcast services and software distribution. However, security is required to prevent theft, and to ensure revenue generation from authorized recipients. We have designed the Secure ECommerce Transactions for Multicast Services (SETMS) architectural framework, to secure ecommerce sessions for multicast environments. The SETMS framework provides authentication of host through the HIP protocol, authorization of subscriber and his/her e-payments through a variant of the 2KP protocol, a procedure to account for the subscriber?s resource consumption, and support for nonrepudiation of principal parties through PKI. The SETMS framework has been formally validated using the AVISPA tool.