Zoom Phone supports secure voice calls for connections between the Zoom Cloud and the Zoom desktop client, mobile app, web browser/client, and supported SIP devices. During call setup, Zoom Phone uses SIP over TLS 1.2 with Advanced Encryption Standard (AES) 256-bit algorithm for these connections. The Zoom desktop client, mobile app, and web browser/client connections encrypt call media to the Zoom Cloud using SRTP with AES 256-bit encryption algorithm. SIP devices configured with SRTP use AES-128 or AES-256 bit algorithm to encrypt call media for connections to the Zoom Cloud, otherwise unencrypted RTP is used as a fallback. 

Important: By default, AES-128 bit encryption is enabled for call media transmitted by supported SIP devices. Admins can upgrade devices to AES-256 bit encryption using the web portal. Fax lines may not support full encryption.

This article covers:

• Zoom Phone desktop client and mobile app
• Zoom Phone devices
  • Upgrading to AES-256 bit encryption
  • Downgrading to AES-128 bit encryption

Zoom Phone desktop client and mobile app

Zoom Phone supports SIP signaling between client and/to server over TLS1.2 with AES-256 bit encryption. Media call is transported and protected by SRTP with AES-256 encryption. 

Zoom Phone devices

Zoom Phone supports standards-based encryption using SIP over TLS 1.2 Advanced Encryption Standard (AES) 256-bit algorithm for calls and during phone provisioning sessions. In addition, call media is transported and protected by SRTP with AES-128 algorithm for all devices. Zoom Phone admins can upgrade to AES-256 bit encryption for supported devices. Learn more about certified devices.

Upgrading to AES-256 bit encryption

Admins can upgrade specific models in a site to use AES-256 bit encryption.

1. Sign in to the Zoom web portal.
2. In the navigation menu, click Phone System Management then Company Info.
3. If you have multiple sites, click the name of the site you want to edit.
4. Click the Settings tab.
5. In the Security section, click Add.
6. Select a brand and model, then click Save.
7. Repeat steps 5 and 6 to add more devices.

Downgrading to AES-128 bit encryption

If you previously upgraded to AES-256 bit encryption, you can downgrade to AES-128 bit.

1. Sign in to the Zoom web portal.
2. In the navigation menu, click Phone System Management then Company Info.
3. If you have multiple sites, click the name of the site you want to edit.
4. Click the Settings tab.
5. In the Security section, click the ✖ icon to remove a model and downgrade it to AES-128 bit encryption.