End-to-End Encrypted Messaging

This exciting resource introduces the core technologies that are used for Internet messaging. The book explains how Signal protocol, the cryptographic protocol that currently dominates the field of end to end encryption (E2EE) messaging, is implemented and addresses privacy issues related to E2EE messengers. The Signal protocol and its application in WhatsApp is explored in depth, as well as the different E2EE messengers that have been made available in the last decade are also presented, including SnapChat. It addresses the notion of self-destructing messages (as originally introduced by SnapChat) and the use of metadata to perform traffic analysis. End-to-End Encrypted Messaging Contents Preface Acknowledgments Chapter 1 Introduction References Chapter 2 Internet Messaging 2.1 INTRODUCTION 2.2 E-MAIL 2.2.1 Internet Message Format 2.2.2 E-Mail Protocols 2.3 INSTANT MESSAGING 2.4 FINAL REMARKS References Chapter 3 Cryptographic Techniques 3.1 INTRODUCTION 3.1.1 Cryptology 3.1.2 Cryptographic Systems 3.1.3 Historical Background Information 3.2 CRYPTOSYSTEMS 3.2.1 Unkeyed Cryptosystems 3.2.2 Secret Key Cryptosystems 3.2.3 Public Key Cryptosystems 3.3 CERTIFICATE MANAGEMENT 3.3.1 Introduction 3.3.2 X.509 Certif cates 3.3.3 OpenPGP Certif cates 3.3.4 State of the Art 3.4 FINAL REMARKS References Chapter 4 Secure Messaging 4.1 THREATS AND ATTACKS 4.1.1 Passive Attack 4.1.2 Active Attacks 4.2 ASPECTS AND NOTIONS OF SECURITY 4.3 FINAL REMARKS References Chapter 5 OpenPGP 5.1 ORIGINS AND HISTORY 5.2 TECHNOLOGY 5.2.1 Preliminary Remarks 5.2.2 Key ID 5.2.3 Message Format 5.2.4 PGP/MIME 5.2.5 Cryptographic Algorithms 5.2.6 Message Processing 5.2.7 Key Management 5.3 WEB OF TRUST 5.3.1 Keyrings 5.3.2 Trust Establishment 5.3.3 Key Revocation 5.3.4 Key Servers 5.4 SECURITY ANALYSIS 5.4.1 Specif cation 5.4.2 Implementations 5.5 FINAL REMARKS References Chapter 6 S/MIME 6.1 ORIGINS AND HISTORY 6.2 TECHNOLOGY 6.2.1 Message Formats 6.2.2 Cryptographic Algorithms 6.2.3 Signer Attributes 6.2.4 Enhanced Security Services 6.3 CERTIFICATES 6.4 SECURITY ANALYSIS 6.5 FINAL REMARKS References Chapter 7 Evolutionary Improvements 7.1 WKD AND WKS 7.2 DNS-BASED DISTRIBUTION OF PUBLIC KEYS 7.3 OPPORTUNISTIC ENCRYPTION 7.3.1 Autocrypt 7.3.2 p≡p 7.4 WEB-BASED SOLUTIONS 7.5 FINAL REMARKS References Chapter 8 OTR 8.1 ORIGINS AND HISTORY 8.2 TECHNOLOGY 8.2.1 OTR AKE 8.2.2 Diff e-Hellman Ratchet 8.2.3 Message Processing 8.3 SECURITY ANALYSISIn 2011, a group of researchers from 8.4 FINAL REMARKS References Chapter 9 Signal 9.1 ORIGINS AND HISTORY 9.2 TECHNOLOGY 9.2.1 Key Agreement and Session Establishment 9.2.2 Double Ratchet Mechanism 9.2.3 Authentication Ceremony 9.2.4 Group Messaging 9.3 SECURITY ANALYSIS 9.4 IMPLEMENTATIONS 9.4.1 Viber 9.4.2 Wire 9.4.3 Riot 9.5 FINAL REMARKS References Chapter 10 WhatsApp 10.1 ORIGINS AND HISTORY 10.2 IMPLEMENTATION DETAILS 10.2.1 Transport Layer Security and Complementary Technologies 10.2.2 Cryptographic Algorithms and Key Generation 10.2.3 Message Attachments 10.2.4 Group Messaging 10.3 SECURITY ANALYSIS 10.4 FINAL REMARKS References Chapter 11 Other E2EE Messengers 11.1 IMESSAGE 11.2 WICKR 11.3 THREEMA 11.4 TELEGRAM References Chapter 12 Privacy Issues 12.1 INTRODUCTION 12.2 SELF-DESTRUCTING MESSAGING 12.3 ONLINE PRESENCE INDICATION 12.4 FINAL REMARKS References Chapter 13 Conclusions and Outlook References Appendix A Mathematical Notation Appendix B Abbreviations and Acronyms About the Author Index This book introduces the core technologies that are used for Internet messaging. The major cryptographic techniques that are used for secure and end to end encryption (E2EE) messaging on the Internet are explored. The notion of “secure” and E2EE messaging and various approaches to address it is discussed. A comprehensive treatment of Pretty Good Privacy (PGP) and OpenPGP as well as Secure/Multipurpose Internet Mail Extensions (S/MIME) is given, as well as the evolutionary improvements to PGP/OpenPGP and S/MIME that have been proposed in the past. The different E2EE messengers that have been made available in the last decade are provided and what Signal protocol that is core to E2EE messaging today. The book explains how the Signal protocol is implemented in WhatsApp, and addresses privacy issues related to E2EE messengers. It addresses the notion of self-destructing messages (as originally introduced by SnapChat) and the use of metadata to perform traffic analysis.