Secure Real-Time Transport Protocol (SRTP)

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Secure real-time transport protocol (SRTP) is a protocol for secure delivery of voice and video services over an IP network.

• is an extension to real-time transport protocol (RTP)
• used in VoIP, video teleconferencing, streaming video, and push-to-talk functionality
• provides confidentiality, authentication, and integrity for data in unicast and multicast
• uses
  • AES in counter mode for encryption
  • HMAC-SHA1 or HMAC-MD5 for data integrity and authentication
• defends against replay attacks
  • by using a sequence number for each packet
  • receiver maintains the sequence number of each previously received packet and accepts a new packet only if the packet has not been previously received
• uses UDP port 5004 by default