TESLA@ the Timed Efficient Stream Loss-tolerant Authentication protocol@ provides source authentication in multicast scenarios. TESLA is an efficient protocol with low communication and computation overhead that scales to large numbers of receivers and also tolerates packet loss. TESLA is based on loose time synchronization between the sender and the receivers. Source authentication is realized in TESLA by using Message Authentication Code (MAC) chaining. The use of TESLA within the Secure Real-time Transport Protocol (SRTP) has been published@ targeting multicast authentication in scenarios where SRTP is applied to protect the multimedia data. This solution assumes that TESLA parameters are made available by out-of-band mechanisms. This document specifies payloads for the Multimedia Internet Keying (MIKEY) protocol for bootstrapping TESLA for source authentication of secure group communications using SRTP. TESLA may be bootstrapped using one of the MIKEY key management approaches@ e.g.@ by using a digitally signed MIKEY message sent via unicast@ multicast@ or broadcast.