🟦Contents

1. Introduction

1.1 Outline 1.1.1 E2E Encryption for Zoom Meetings

2. Background and Security Goals

2.1 Limitations

3. User Identity and Key Management

3.1 Non-Cryptographic Identity at Zoom

3.2 Cryptographic User Identity

3.3 Displaying Identity

3.3.1 Identifying Accounts

3.3.2 Identifying Users

3.4 Multi-Device Support

3.4.1 Per-User Keys

3.4.2 Backup Keys

3.4.3 Escrow Keys

3.4.1 Lockdown Mode

3.5 Consistent Identities With Sighchains

3.5.1 Sighchains

3.5.2 Overview of Sighchain Types

3.5.3 User Sighchains

3.5.4 Email Sighchains

3.5.5 Account Sighchains

3.5.6 ADN Sighchains

3.5.7 Membership Sighchains

3.6 Sighchain Fingerprints

3.7 Client Key Management

3.7.1 Storing Secret Keys on Device

3.7.2 Device Management Interface

3.8 Account Escrow

3.8.1 Escrow Administrators and the EA Sighchain

3.8.2 Users’ Escrow Device Management

3.8.3 EA Permissions

3.8.4 User Recovery

3.8.5 Legal Discovery

3.9 Highlighting Untrusted Devices with Contact Sync

3.10 Compromise Prevention for Device Provisioning

3.11 Security Properties

3.11.1 MitM Between a User’s Devices

3.11.2 MitM Between Different Users

3.11.3 Integrity

3.11.4 Security Limitations

3.11.5 Privacy Limitations

4. Transparency Tree

4.1 Zoom Transparency Tree

4.2 Integration Details

4.2.1 ZTT Auditing

4.2.2 Provisioning

4.2.3 Self-Audit and Refresh

4.2.4 Validating User Identity

4.2.5 Contact List Updates

4.3 Security Properties

5 Identity Provider Attestations

5.1 Associating Accounts with Identity Providers

5.2 IDP Attestations 5.3 Updating Snapshots

5.4 Validating IDP Attestations

5.5 Zoom Identity Snapshots

5.6 Security Properties

6. Encryption for Zoom Mail Service

6.1 Encrypted Email Protocol

6.2 Emails to Users without Devices

6.3 Emails to and from External Users

6.4 Mailing Lists 6.5 Calendar Email Integration

6.6 Encrypting Non-Email Data

6.7 Security Properties

6.7.1 Spam Detection and Contact Monitoring

7. Encryption for Zoom Meetings

7.1 Zoom Meetings

7.2 Enhanced Encryption

7.3 End-to-End Encryption

7.3.1 Security Goals

7.4 System Components

7.5 Cryptographic Algorithms

7.5.1 Signing

7.5.2 Authenticated Public-Key Encryption

7.6 Join/Leave Protocol flow

7.6.1 Server Key Certificate Chains

7.6.2 Participant Key Generation

7.6.3 Leader Join

7.6.4 Participant Join (Leader)

7.6.5 Participant Join (Non-Leader)

7.6.6 Key Rotation

7.6.7 Leader Participant List

7.6.8 Liveness

7.6.9 Locked Meetings

7.6.10 Meeting Teardown

7.7 Meeting Leader Security Code

7.8 E2E Encryption for Breakout Rooms

7.9 Abuse Management and Reporting

7.10 IDP Attestations for E2EE Meetings

7.11 E2EE Meetings with Cryptographic Identity

7.12 Security Properties for E2EE Meetings

7.12.1 Areas to Improve

8. Encryption for Zoom Phone

8.1 E2EE Zoom Phone Calls

8.1.1 Join/Leave Protocol

8.1.2 Phone Security Code

8.2 Advanced Encryption for Voicemail

8.2.1 Security Properties

A. Release Schedule

B Understanding Multiple Devices

B.1 A Claim about Device Equivalence Classes

C. Cake-AES

C.1 Encryption

C.2 Decryption

C.3 Random-Access Decryption