After presenting our work at Real World Crypto 2018 [1] and seeing the enormous press coverage, we want to get two things straight: 1. Most described weaknesses are only exploitable by the malicious server or by knowing a large secret number and thereby the protocols are still very secure (what we wrote in the paper but some newspapers did not adopt) and 2. we see ways to enhance the WhatsApp protocol without breaking its features.
We are of course very happy that our research reached so many people and even though IT security and cryptography are often hard to understand for outsiders, Andy Greenberg [2], Patrick Beuth [3] and other journalists [4,5,6,7,8] wrote articles that were understandable on the one hand and very accurate and precise on the other hand. In contrast to this, we also saw some inaccurate articles [9,10] that fanned fear and greatly diverged in their description from what we wrote in our paper. We expected this from the boulevard press in Germany and therefore asked them to stick to the facts when they were contacting us. But none of the worst two articles' [9,10] authors contacted us in advance. Since our aim was never to blame any application or protocol but rather we wanted to encourage the developers to enhance the protocols, it contradicts our aim that WhatsApp and Signal are partially declared attackable by "anyone" "easily" [9,10].
Against this background, we understand Moxie's vexation about certain headlines that were on the Internet in the last days [11]. However, we believe that the ones who understand the weaknesses, comprehend that only the malicious server can detectably make use of them (in WhatsApp) or the secret group ID needs to be obtained from a member (in Signal). As such, we want to make clear that our paper does not primarily focus on the description of weaknesses but presents a new approach for analyzing and evaluating the security of group instant messaging protocols. Further we propose measures to enhance the analyzed protocols. The description of the protocols' weaknesses is only one part of the evaluation of our analysis approach and thereby of the investigation of real world protocols. This is the scientific contribution of our paper. The practical contribution of the analyzed messengers, which is the communication confidentiality for billion users (in most cases), is great and should be noted. Therefore we believe that being Signal, WhatsApp, or Threema by applying encryption to all messages and consequently risking research with negative results is much better than being a messenger that does not encrypt group messages end-to-end at all. We do not want to blame messengers that are far less secure (read Moxie's post [11] if you are interested).
Finally we want note that applying security measures according to the ticket approach (as we call it in the paper [12]) to the invitation links would solve the issues that Facebook's security head mentioned in his reply [13] on our findings. To our knowledge, adding authenticity to group update messages would not affect invitation links: If no invitation link was generated for a group, group members should only accept joining users if they were added by an authentic group update message. As soon as a group invitation link was generated, all joining users would need to be accepted as new group members with the current design. However there are plenty ways how WhatsApp could use invitation links without endowing the server with the power to manage groups without the group admins' permission:
One approach would be generating the invitation links secretly and sharing them without the knowledge of the server. An invitation link could then contain a secret ticket for the group and the ID of the group. As soon as a user, who received the link, wants to join the group, she can request the server with the group ID to obtain all current group members. The secret ticket can now be sent to all existing group members encrypted such that the legitimate join can be verified.
Of course this would require engineering but the capability of WhatsApp, shipping drastic protocol updates, can be assumed since they applied end-to-end encryption in the first place.
[1] https://www.youtube.com/watch?v=i5i38WlHfds
[2] https://www.wired.com/story/whatsapp-security-flaws-encryption-group-chats/
[3] http://www.spiegel.de/netzwelt/apps/whatsapp-gruppenchats-schwachstelle-im-verschluesselungs-protokoll-a-1187338.html
[4] http://www.sueddeutsche.de/digital/it-sicherheit-wie-fremde-sich-in-whatsapp-gruppenchats-einladen-koennen-1.3821656
[5] https://techcrunch.com/2018/01/10/security-researchers-flag-invite-bug-in-whatsapp-group-chats/
[6] http://www.telegraph.co.uk/technology/2018/01/10/whatsapp-bug-raises-questions-group-message-privacy/
[7] http://www.handelsblatt.com/technik/it-internet/verschluesselung-umgangen-forscher-finden-sicherheitsluecke-bei-whatsapp/20836518.html
[8] https://www.heise.de/security/meldung/WhatsApp-und-Signal-Forscher-beschreiben-Schwaechen-verschluesselter-Gruppenchats-3942046.html
[9] https://www.theinquirer.net/inquirer/news/3024215/whatsapp-bug-lets-anyone-easily-infiltrate-private-group-chats
[10] http://www.dailymail.co.uk/sciencetech/article-5257713/WhatsApp-security-flaw-lets-spy-private-chats.html
[11] https://news.ycombinator.com/item?id=16117487
[12] https://eprint.iacr.org/2017/713.pdf
[13] https://twitter.com/alexstamos/status/951169036947107840
Further articles:
- Matthew Green's blog post: https://blog.cryptographyengineering.com/2018/01/10/attack-of-the-week-group-messaging-in-whatsapp-and-signal/
- Schneier on Security: https://www.schneier.com/blog/archives/2018/01/whatsapp_vulner.html
- Bild: http://www.bild.de/digital/smartphone-und-tablet/whatsapp/whatsapp-sicherheitsluecke-in-gruppenchats-54452080.bild.html
- Sun: https://www.thesun.co.uk/tech/5316110/new-whatsapp-bug-how-to-stay-safe/
More articlesWe are of course very happy that our research reached so many people and even though IT security and cryptography are often hard to understand for outsiders, Andy Greenberg [2], Patrick Beuth [3] and other journalists [4,5,6,7,8] wrote articles that were understandable on the one hand and very accurate and precise on the other hand. In contrast to this, we also saw some inaccurate articles [9,10] that fanned fear and greatly diverged in their description from what we wrote in our paper. We expected this from the boulevard press in Germany and therefore asked them to stick to the facts when they were contacting us. But none of the worst two articles' [9,10] authors contacted us in advance. Since our aim was never to blame any application or protocol but rather we wanted to encourage the developers to enhance the protocols, it contradicts our aim that WhatsApp and Signal are partially declared attackable by "anyone" "easily" [9,10].
Against this background, we understand Moxie's vexation about certain headlines that were on the Internet in the last days [11]. However, we believe that the ones who understand the weaknesses, comprehend that only the malicious server can detectably make use of them (in WhatsApp) or the secret group ID needs to be obtained from a member (in Signal). As such, we want to make clear that our paper does not primarily focus on the description of weaknesses but presents a new approach for analyzing and evaluating the security of group instant messaging protocols. Further we propose measures to enhance the analyzed protocols. The description of the protocols' weaknesses is only one part of the evaluation of our analysis approach and thereby of the investigation of real world protocols. This is the scientific contribution of our paper. The practical contribution of the analyzed messengers, which is the communication confidentiality for billion users (in most cases), is great and should be noted. Therefore we believe that being Signal, WhatsApp, or Threema by applying encryption to all messages and consequently risking research with negative results is much better than being a messenger that does not encrypt group messages end-to-end at all. We do not want to blame messengers that are far less secure (read Moxie's post [11] if you are interested).
Finally we want note that applying security measures according to the ticket approach (as we call it in the paper [12]) to the invitation links would solve the issues that Facebook's security head mentioned in his reply [13] on our findings. To our knowledge, adding authenticity to group update messages would not affect invitation links: If no invitation link was generated for a group, group members should only accept joining users if they were added by an authentic group update message. As soon as a group invitation link was generated, all joining users would need to be accepted as new group members with the current design. However there are plenty ways how WhatsApp could use invitation links without endowing the server with the power to manage groups without the group admins' permission:
One approach would be generating the invitation links secretly and sharing them without the knowledge of the server. An invitation link could then contain a secret ticket for the group and the ID of the group. As soon as a user, who received the link, wants to join the group, she can request the server with the group ID to obtain all current group members. The secret ticket can now be sent to all existing group members encrypted such that the legitimate join can be verified.
Of course this would require engineering but the capability of WhatsApp, shipping drastic protocol updates, can be assumed since they applied end-to-end encryption in the first place.
[1] https://www.youtube.com/watch?v=i5i38WlHfds
[2] https://www.wired.com/story/whatsapp-security-flaws-encryption-group-chats/
[3] http://www.spiegel.de/netzwelt/apps/whatsapp-gruppenchats-schwachstelle-im-verschluesselungs-protokoll-a-1187338.html
[4] http://www.sueddeutsche.de/digital/it-sicherheit-wie-fremde-sich-in-whatsapp-gruppenchats-einladen-koennen-1.3821656
[5] https://techcrunch.com/2018/01/10/security-researchers-flag-invite-bug-in-whatsapp-group-chats/
[6] http://www.telegraph.co.uk/technology/2018/01/10/whatsapp-bug-raises-questions-group-message-privacy/
[7] http://www.handelsblatt.com/technik/it-internet/verschluesselung-umgangen-forscher-finden-sicherheitsluecke-bei-whatsapp/20836518.html
[8] https://www.heise.de/security/meldung/WhatsApp-und-Signal-Forscher-beschreiben-Schwaechen-verschluesselter-Gruppenchats-3942046.html
[9] https://www.theinquirer.net/inquirer/news/3024215/whatsapp-bug-lets-anyone-easily-infiltrate-private-group-chats
[10] http://www.dailymail.co.uk/sciencetech/article-5257713/WhatsApp-security-flaw-lets-spy-private-chats.html
[11] https://news.ycombinator.com/item?id=16117487
[12] https://eprint.iacr.org/2017/713.pdf
[13] https://twitter.com/alexstamos/status/951169036947107840
Further articles:
- Matthew Green's blog post: https://blog.cryptographyengineering.com/2018/01/10/attack-of-the-week-group-messaging-in-whatsapp-and-signal/
- Schneier on Security: https://www.schneier.com/blog/archives/2018/01/whatsapp_vulner.html
- Bild: http://www.bild.de/digital/smartphone-und-tablet/whatsapp/whatsapp-sicherheitsluecke-in-gruppenchats-54452080.bild.html
- Sun: https://www.thesun.co.uk/tech/5316110/new-whatsapp-bug-how-to-stay-safe/
- Hack App
- Pentest Tools Download
- Top Pentest Tools
- Pentest Tools Apk
- Black Hat Hacker Tools
- Hacking Tools Software
- Hacking Tools For Pc
- Hacking Tools Name
- Pentest Recon Tools
- Hacking Tools Pc
- Beginner Hacker Tools
- Hacking Tools For Windows 7
- Hacking Tools And Software
- World No 1 Hacker Software
- Hacking Tools Online
- Hacking Tools Windows
- Pentest Tools For Ubuntu
- Hacking Tools
- Nsa Hack Tools
- Hacker Tools Linux
- Best Hacking Tools 2019
- Pentest Tools For Mac
- Nsa Hack Tools Download
- Hacker Tools Software
- Black Hat Hacker Tools
- Pentest Tools Open Source
- Best Hacking Tools 2019
- Pentest Tools Nmap
- Nsa Hack Tools Download
- Pentest Tools Apk
- Hacking Tools For Kali Linux
- Pentest Tools For Windows
- Hack Tools Online
- Hack Tools For Windows
- Best Pentesting Tools 2018
- Pentest Tools Open Source
- Physical Pentest Tools
- Ethical Hacker Tools
- Hacking Tools Windows 10
- Hack Tool Apk No Root
- Hack Tools Online
- Hacker Tools For Pc
- Hacks And Tools
- Hack Tool Apk No Root
- Hacker Tools 2020
- Pentest Tools Alternative
- Nsa Hack Tools Download
- Pentest Tools Subdomain
- Github Hacking Tools
- Hacker Tools 2020
- Hak5 Tools
- Hacking Tools And Software
- Pentest Tools Online
- Hacker Tools 2019
- Hacker Tools 2020
- Hack Rom Tools
- How To Make Hacking Tools
- Tools Used For Hacking
- Pentest Tools For Ubuntu
- Pentest Tools Linux
- Computer Hacker
- Github Hacking Tools
- Pentest Tools List
- Pentest Tools
- Pentest Tools
- Hack Tool Apk
- Hacking Tools Software
- Pentest Reporting Tools
- Pentest Tools Linux
- Hacker Tools Github
- Hacking Tools Usb
- Best Pentesting Tools 2018
- Tools 4 Hack
- How To Hack
- How To Hack
- Best Pentesting Tools 2018
- Pentest Tools Open Source
- Pentest Tools Download
- Hacker
- Pentest Tools Nmap
- Pentest Tools Windows
- Bluetooth Hacking Tools Kali
- Hack Tools For Ubuntu
- Install Pentest Tools Ubuntu
- Pentest Tools List
- Hack Tools Github
- Hacking Tools For Games
- Pentest Tools Github
- How To Install Pentest Tools In Ubuntu
- Hacking Tools Kit
- Pentest Tools Android
- Hacker Tools List
- Hacking Tools Free Download
- Best Hacking Tools 2019
- Pentest Tools For Android
- Hacking Tools Online
- Hacking Tools For Kali Linux
- Usb Pentest Tools
- Pentest Tools Free
- Hacking Tools Name
- Hacks And Tools
- Hacking Tools Free Download
- Pentest Tools Linux
- Hack Tools For Ubuntu
- Tools Used For Hacking
- Pentest Tools
- Pentest Tools Url Fuzzer
- Pentest Tools Port Scanner
- How To Make Hacking Tools
- Nsa Hack Tools Download
- Hacker Search Tools
- Hacking Tools Hardware
- Hacking Tools Mac
- Hack Website Online Tool
- Hack Tools Pc
- How To Make Hacking Tools
- Nsa Hack Tools
- Hack And Tools
- Hack Apps
- Hack Tools
- Hacker Tools 2019
- Hacker Security Tools
- Pentest Recon Tools
- Tools 4 Hack
- Hack Tools Pc
- Hacker Tools For Pc
- Hacking Tools Pc
- Hacker Tools Free
- Tools Used For Hacking
More articles