Merge pull request #75 from nextleap-project/talk-brussels

talk: brussels OpenPGP summit

2018_talk_brussels_oct_20/Makefile

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2018_talk_brussels_oct_20/talk.css

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2018_talk_brussels_oct_20/talk.rst

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+.. title: Securing Autocrypt against active attacks
+
+
+----
+
+Securing Autocrypt against active attacks
+=========================================
+
+presented at OpenPGP Summit Brussels 2018
+by azul@merlinux.eu
+
+
+----
+
+CounterMitM
+===========
+
+- developed as part of NEXTLEAP research
+
+- based on Autocrypt Level 1
+
+- Here: Focus on OpenPGP based ideas
+
+----
+
+Autocrypt Level 1
+=================
+
+- prevent passive collection of email content
+
+- usability centered
+
+- replace clear text mail
+
+- Autocrypt gossip to make encrypted reply to all easy.
+
+----
+
+Active Attacks against Autocrypt Level 1
+========================================
+
+- Machine in the middle attack (MitM)
+
+- In band key transfer = easier for MitM
+
+- replace Autocrypt headers with MitM keys
+
+- continuously reencrypt
+
+- end attack by reencrypting without replacing headers
+
+----
+
+Verify Contacts based on QR codes
+==================================
+
+.. image:: img/delta-scan.png
+
+- one person shows the QR code, other person scans.
+
+- works with laptop & mobile
+
+----
+
+Underlying mechanism
+====================
+
+- similar to fingerprint printouts
+  with secret to authenticate recipient
+
+- requires confidentiallity of QR code
+
+- system messages
+
+- currently using Autocrypt headers for key retrieval
+
+  could use: keyserver, wkd, etc.
+
+----
+
+Securing Group Communication
+============================
+
+- pairwise verification does not scale
+
+- web of trust leaks the social graph
+
+- gossip consistency:
+  error cases instead of use cases
+
+----
+
+Verified groups
+===============
+
+- use cases:
+  - join group
+  - add member to group
+
+- flow:
+  - verify contact
+  - send introduction message
+
+----
+
+Verified groups: Properties
+===========================
+
+- fully connected verification graph
+
+- can replace gossip
+
+----
+
+Verified groups: Considerations
+===============================
+
+- Reuse verifications accross groups?
+
+  - + easier to create new groups
+
+  - + faster recovery from lost device
+
+  - - combined attack of provider and verified contact
+
+  - - less incentitive to verify contacts
+
+
+----
+
+Verified groups: Infiltrator attack
+===================================
+
+- Alice, Bob and Egon
+
+- Egon verified Alice and Bob, started the group
+
+- Egon collaborates with MitM attacker and introduced MitM keys
+
+- Attacker can MitM mails between Alice and Bob
+
+- Evidence of Egons involvement in signed messages
+
+----
+
+
+History verification
+====================
+
+- use case:
+  Verifying existing contact
+
+- flow:
+  - verify contact
+  - exchange message-key log
+
+- goal: detect previous MitM attacks
+
+----
+
+More
+====
+
+- Claimchains:
+  Privacy-preserving decentralized public key distribution based on
+  cross-referencing hash chains.
+  https://claimchain.github.io/
+
+- Gossip consistency
+
+- Using DKIM to verify Autocrypt headers
+
+- https://github.com/nextleap-project/countermitm