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Out of band verification of key fingerprints is necessary to protect against a malicious server. Users are encouraged to tweet their public keys and verify in p

by zmanian 11y ago

Out of band verification of key fingerprints is necessary to protect against a malicious server. Users are encouraged to tweet their public keys and verify in person. We don't have any mechanism other than trusting Whisper Systems that their client binaries matches the sources. The truly paranoid could be their own client application from source.

acqq 11y ago
Do you talk about TextSecure or PGP when you talk about "out of band verification of key fingerprints"? I'm talking about TextSecure. And I'm not interested in the client side, but in the server side of the security. I assume I can rebuild the client using the sources and compare their client with my build. What I can't assume is that their servers aren't, for example, infested by some state security malware which takes over the control. I want the protocols that work even when the server is subverted.
- zmanian 11y ago
  Textsecure has out of band fingerprint verification. There are that are working on eliminating the need for central server for message delivery and key server roles like https://briarproject.org/ https://briarproject.org/ https://github.com/muttr/whitepaper/blob/master/README.md https://github.com/muttr/whitepaper/blob/master/README.md
  - acqq 11y ago
    I don't see what these other projects you link to change to the TextSecure protocol. What I'm interested in is this part of the protocol description: https://whispersystems.org/blog/asynchronous-security/ https://whispersystems.org/blog/asynchronous-security/ "At registration time, the TextSecure client preemptively generates 100 signed key exchange messages and sends them to the server. We call these “prekeys.” A client that wishes to send a secure message to a user for the first time can now: - Connect to the server and request the destination’s next “prekey.”" Etc. How is this not giving the server chance to insert its own keys and not the ones user generated? What the QR code thing is actually doing? From what I understand, the TextSecure/Signal in one way or another send your contacts to the server and the server stores "prekeys" and delivers them to the clients. Where is any analysis that says that all this stuff doesn't mean that we have to trust that the server is not evil? If the QR code means "yes it's the person you want to communicate to" but the contacts are on the server and the prekeys are delivered from the server, am I any better? I need to read somewhere that the server is not weak point and why it is not. Any link?
    - caf 11y ago
      How is this not giving the server chance to insert its own keys and not the ones user generated? Because the server can't sign the key exchange messages - the private key is generated on the client and never leaves it.
      - acqq 11y ago
        So would everything be safe if the server is controlled by an attacker and the attacker can also act as MtM for the communication data? Is there any analysis/verification of the full protocol and/or whole process of TextSecure/Signal as they are commonly used? I'd greatly appreciate the link.

by zmanian 11y ago

acqq 11y ago

Do you talk about TextSecure or PGP when you talk about "out of band verification of key fingerprints"? I'm talking about TextSecure. And I'm not interested in the client side, but in the server side of the security. I assume I can rebuild the client using the sources and compare their client with my build. What I can't assume is that their servers aren't, for example, infested by some state security malware which takes over the control. I want the protocols that work even when the server is subverted.

zmanian 11y ago
Textsecure has out of band fingerprint verification. There are that are working on eliminating the need for central server for message delivery and key server roles like https://briarproject.org/ https://briarproject.org/ https://github.com/muttr/whitepaper/blob/master/README.md https://github.com/muttr/whitepaper/blob/master/README.md
- acqq 11y ago
  I don't see what these other projects you link to change to the TextSecure protocol. What I'm interested in is this part of the protocol description: https://whispersystems.org/blog/asynchronous-security/ https://whispersystems.org/blog/asynchronous-security/ "At registration time, the TextSecure client preemptively generates 100 signed key exchange messages and sends them to the server. We call these “prekeys.” A client that wishes to send a secure message to a user for the first time can now: - Connect to the server and request the destination’s next “prekey.”" Etc. How is this not giving the server chance to insert its own keys and not the ones user generated? What the QR code thing is actually doing? From what I understand, the TextSecure/Signal in one way or another send your contacts to the server and the server stores "prekeys" and delivers them to the clients. Where is any analysis that says that all this stuff doesn't mean that we have to trust that the server is not evil? If the QR code means "yes it's the person you want to communicate to" but the contacts are on the server and the prekeys are delivered from the server, am I any better? I need to read somewhere that the server is not weak point and why it is not. Any link?
  - caf 11y ago
    How is this not giving the server chance to insert its own keys and not the ones user generated? Because the server can't sign the key exchange messages - the private key is generated on the client and never leaves it.
    - acqq 11y ago
      So would everything be safe if the server is controlled by an attacker and the attacker can also act as MtM for the communication data? Is there any analysis/verification of the full protocol and/or whole process of TextSecure/Signal as they are commonly used? I'd greatly appreciate the link.