SRTP vs RTP: What’s the Difference and Why It Matters for VoIP Security

When you make a VoIP call, your voice travels as data packets over the internet using the RTP, Real-Time Transport Protocol, the standard for delivering audio and video over IP networks. Also known as Real-time Transport Protocol, it’s fast, efficient, and built into nearly every phone system. But here’s the catch: RTP doesn’t encrypt anything. Your call could be intercepted, replayed, or even altered by someone on the same network. That’s where SRTP, Secure Real-time Transport Protocol, an extension of RTP that adds encryption, authentication, and replay protection. It’s the difference between sending a postcard and locking it in a safe before mailing it. If you’re using VoIP for business, healthcare, or even just remote work, understanding SRTP vs RTP isn’t optional—it’s essential.

Most modern VoIP systems use SRTP by default, but not all do. Some older IP phones, free softphones, or poorly configured SIP trunks still rely on plain RTP. That means your calls might sound clear, but they’re not safe. Hackers can use free tools to capture and listen to unencrypted calls on public Wi-Fi, in shared office networks, or even through compromised routers. SRTP fixes this by encrypting the audio stream with AES, validating each packet with a message authentication code, and preventing replay attacks. It’s not magic—it’s math. And that math is why companies like RingCentral, Zoom for Healthcare, and Nextiva all require SRTP for HIPAA compliance and enterprise-grade security.

SRTP doesn’t slow down your calls. It adds almost no extra bandwidth, and modern processors handle encryption in the background without noticeable delay. But if your provider doesn’t support SRTP, or your IP phone is stuck on an outdated firmware, you’re still vulnerable. Look for terms like "SRTP enabled," "AES-128 encryption," or "secure media stream" in your VoIP settings. If you’re setting up a FreePBX system or configuring a softphone, double-check the codec and transport settings—RTP might be the default, and you’ll need to manually switch to SRTP.

It’s not just about compliance. Think about your customer calls, internal team chats, or even personal video conferences. Would you want strangers listening in? SRTP is the baseline. RTP is the old way. And in 2025, using RTP without SRTP is like leaving your front door wide open and hoping no one walks in.

Below, you’ll find real-world guides on VoIP security, encryption best practices, codec choices, and how to harden your system against eavesdropping and toll fraud. These aren’t theory pieces—they’re step-by-step fixes from businesses that learned the hard way.