4 ms·

Checking URLs passed in messages isn't incompatible with secure communication. It's easy enough to look at a text message that's going to be sent and break it i

Checking URLs passed in messages isn't incompatible with secure communication. It's easy enough to look at a text message that's going to be sent and break it into parts (URL and non-URL). Encrypt point-to-point the non-URL parts, and encrypt the URL parts such that the central servers can read them (and verify that they're not pointing to bad stuff, which is a very valuable service to provide to the vast number of readers). We might find somewhere in Skype's ToS a reference to URL checking, for any URLs you send through the service. The URL checks could also be anonymized.

betterunix 13y ago
"Checking URLs passed in messages isn't incompatible with secure communication" I guess that depends on your definition of "security," and perhaps of "practicality." Where I'm from (i.e. a grad student whose research is on practical secure multiparty computation), a practical system for checking URLs in a privacy-preserving fashion is still very much a research topic. "It's easy enough to look at a text message that's going to be sent and break it into parts (URL and non-URL). Encrypt point-to-point the non-URL parts, and encrypt the URL parts such that the central servers can read them" How is that secure? Now the third party knows what URLs you are sending in your messages. "The URL checks could also be anonymized." Sure, but that is not what you are seeing here. You would need a mix-net of some kind, one in which the users themselves are participating (to ensure that there is at least one honest party). It is technically possible...but you're not going to see it happen, not any time soon. With the FBI talking about building back doors into everything, what incentive is there for a company like Microsoft to actually make such a secure system? When it comes down to it, most Skype users are too uninformed to even know how their software might betray them. On the other hand, the Justice Department could create plenty of difficulty for Microsoft if they failed to cooperate. Whose side do you think Microsoft will choose?
- rossjudson 13y ago
  I'm not arguing that the communications stay theoretically secure. If there's any processing going on, they clearly don't. What I'm saying is that you break the message up into risk and non-risky parts, and the risky parts (URLs) can be treated differently. That different treatment is very valuable to the vast majority of users that don't care about complete security, but do care about having their systems compromised. Which "betrayal" is worse -- Skype being able to look at messages, or compromised systems? In terms of implementation, it's interesting to think about the design space.
wnight 13y ago
Actually, being able to tell anything about a message is incompatible with secure communications. Even the fact that there's a URL in there is more than I want you to know. It's all it would have taken to get shot in Iran in 2009. There's a good way to do this though - give the users a local URL classifier and push updates to it. Then the client software is free to block dangerous URLs by default without hurting anyone's privacy. This works, and is used by many AV companies. In fact, because of the way the system is centralized they could be sure the updates would reach users before another message did - providing the same level of safety as scanning the users' messages for them.

betterunix 13y ago

"Checking URLs passed in messages isn't incompatible with secure communication" I guess that depends on your definition of "security," and perhaps of "practicality." Where I'm from (i.e. a grad student whose research is on practical secure multiparty computation), a practical system for checking URLs in a privacy-preserving fashion is still very much a research topic. "It's easy enough to look at a text message that's going to be sent and break it into parts (URL and non-URL). Encrypt point-to-point the non-URL parts, and encrypt the URL parts such that the central servers can read them" How is that secure? Now the third party knows what URLs you are sending in your messages. "The URL checks could also be anonymized." Sure, but that is not what you are seeing here. You would need a mix-net of some kind, one in which the users themselves are participating (to ensure that there is at least one honest party). It is technically possible...but you're not going to see it happen, not any time soon. With the FBI talking about building back doors into everything, what incentive is there for a company like Microsoft to actually make such a secure system? When it comes down to it, most Skype users are too uninformed to even know how their software might betray them. On the other hand, the Justice Department could create plenty of difficulty for Microsoft if they failed to cooperate. Whose side do you think Microsoft will choose?

rossjudson 13y ago
I'm not arguing that the communications stay theoretically secure. If there's any processing going on, they clearly don't. What I'm saying is that you break the message up into risk and non-risky parts, and the risky parts (URLs) can be treated differently. That different treatment is very valuable to the vast majority of users that don't care about complete security, but do care about having their systems compromised. Which "betrayal" is worse -- Skype being able to look at messages, or compromised systems? In terms of implementation, it's interesting to think about the design space.

wnight 13y ago

Actually, being able to tell anything about a message is incompatible with secure communications. Even the fact that there's a URL in there is more than I want you to know. It's all it would have taken to get shot in Iran in 2009. There's a good way to do this though - give the users a local URL classifier and push updates to it. Then the client software is free to block dangerous URLs by default without hurting anyone's privacy. This works, and is used by many AV companies. In fact, because of the way the system is centralized they could be sure the updates would reach users before another message did - providing the same level of safety as scanning the users' messages for them.