Securing Real-Time Communication: An In-Depth Exploration of the SRTP Protocol

5 min read
November 30, 2023

Real-time media streaming is becoming increasingly popular. Thus, keeping sensitive voice and video calls safe from hacking is crucial. The Secure Real-Time Transport Protocol (SRTP) adds encryption, authentication, and replay protection to the Real-time Transport Protocol (RTP). This enables private, tamper-proof conversations over untrusted networks. This article examines how SRTP operates and explains its key role in modern telecom security.

Table of Contents

  1. Definition of Secure Real-Time Transport Protocol (SRTP)
  2. How does SRTP work?
  3. Benefits of using SRTP
  4. The role of SRTP in video conferencing
  5. How Digital Samba's SDK/API leverages SRTP to secure video conferencing
  6. Conclusion

Definition of Secure Real-Time Transport Protocol (SRTP)

The Secure Real-Time Transport Protocol, or SRTP, is a security layer that protects real-time communication and media, such as audio and video, as it travels over the internet. It does this by encrypting the data, rendering it unreadable to anyone except the intended recipient. SRTP also verifies that the data has not been altered. Finally, SRTP prevents replay attacks, where an attacker sends the same data multiple times to deceive the recipient.

How does SRTP work?

SRTP utilises symmetric cryptography with session keys to ensure the integrity and authenticity of RTP packets. For WebRTC, these keys are derived from a DTLS handshake, rather than protocols like MIKEY or SDES. To encrypt the RTP payload, SRTP employs strong encryption methods such as AES. It uses message authentication checks like HMAC-SHA1 for packet verification.

By encrypting payloads and verifying packets, SRTP safeguards against eavesdropping, tampering, and replay attacks. It offers security comparable to IPsec but is specifically tailored for real-time media with low overhead. Essentially, SRTP is a protocol for securing RTP. It maintains high compatibility with RTP and can use the same ports.

SRTP is widely used to protect the confidentiality of media in VoIP, video conferencing, and streaming applications. It can secure RTP sessions over any RTP transport, such as UDP, TCP, or SCTP. With its encryption and lightweight overhead, SRTP is the standard for securing real-time multimedia.

Benefits of using SRTP

The Secure Real-Time Transport Protocol (SRTP) plays a vital role in keeping voice and video calls secure. Here are some key advantages of SRTP:

SRTP plays a crucial role in ensuring the safety and security of real-time applications. Its use of encryption, authentication, and integrity checks acts as a shield against common threats such as eavesdropping, impersonation, and information tampering.

The role of SRTP in video conferencing

SRTP is integral to secure video calling and conferencing. As video conferencing involves transmitting audio and video across various locations, encrypting the streams is vital to prevent unauthorised access. In video conferencing, SRTP:

  • Provides encryption, message verification, and replay attack defence for RTP media streams. It utilises AES encryption to secure media packets with 128 or 256-bit keys. This advanced cryptography prevents the deciphering of intercepted video and audio content.
  • Generates a unique code for each packet using HMAC-SHA1, allowing the receiving device to authenticate packets as unaltered.
  • Protects against replay attacks by identifying and blocking the replay of old packets, thereby preventing denial of service attempts

As meetings increasingly move online, SRTP ensures sensitive discussions remain confidential. Video conferencing has enabled work and remote healthcare, but without encryption, sensitive patient details or business plans could be compromised. SRTP's real-time encryption eliminates this risk.

For users, SRTP operates invisibly yet is crucial. Encryption occurs automatically, requiring no manual configuration, making secure connections effortless. SRTP-enabled apps and devices can communicate securely, safeguarding their users.

With video calling now commonplace, SRTP's role is more vital than ever. Its invisible protection is essential for securing against eavesdropping and tampering, making it an indispensable component for any public or private sector video application.

How Digital Samba's SDK/API leverages SRTP to secure video conferencing

The Digital Samba video conferencing SDK/API integrates the Secure Real-Time Transport Protocol (SRTP) to encrypt video calls from end-to-end. This provides a secure means of transmitting audio and video data streams between call participants over the internet.

The SDK manages the establishment of cryptographic parameters necessary for SRTP. It facilitates key exchanges using DTLS and derives session keys for encrypting/decrypting each media packet. AES encryption is applied to RTP payloads transparently, ensuring confidentiality for media in transit without requiring developers to implement this themselves.

Integrity protection is also handled automatically through SRTP hash functions. Packets are verified to ensure they have not been compromised before being displayed to the user. Replay attack prevention is likewise enabled.

By simplifying the complexities of establishing SRTP sessions, the Digital Samba SDK/API offers developers an accessible way to incorporate secure video conferencing into their applications. End-users benefit from private calls protected against eavesdropping and tampering. The toolkit saves significant development time compared to integrating this encryption directly.


SRTP, or Secure Real-Time Transport Protocol, serves as a specialised security guard for real-time communication. It ensures the protection of shared information, such as voice calls or video chats, from eavesdropping, tampering, and replay attacks. This is achieved through the use of encryption keys and techniques like salting, which are akin to secret codes and special ingredients making the information more difficult to decipher.

While SRTP is not infallible, it is a potent tool for maintaining the privacy and security of real-time communication. When utilised effectively, SRTP can significantly enhance the security of VoIP, video conferencing, and other real-time applications.

To develop a highly secure video conferencing platform, consider using Digital Samba's SDK/API. It is designed with powerful security features to ensure that real-time audio and video signals are transmitted securely from one end to the other. Sign up to get started!

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