Entries Tagged "https"
Page 2 of 2
This is really clever:
Many anticensorship systems work by making an encrypted connection (called a “tunnel”) from the user’s computer to a trusted proxy server located outside the censor’s network. This server relays requests to censored websites and returns the responses to the user over the encrypted tunnel. This approach leads to a cat-and-mouse game, where the censor attempts to discover and block the proxy servers. Users need to learn the address and login information for a proxy server somehow, and it’s very difficult to broadcast this information to a large number of users without the censor also learning it.
Telex turns this approach on its head to create what is essentially a proxy server without an IP address. In fact, users don’t need to know any secrets to connect. The user installs a Telex client app (perhaps by downloading it from an intermittently available website or by making a copy from a friend). When the user wants to visit a blacklisted site, the client establishes an encrypted HTTPS connection to a non-blacklisted web server outside the censor’s network, which could be a normal site that the user regularly visits. Since the connection looks normal, the censor allows it, but this connection is only a decoy.
The client secretly marks the connection as a Telex request by inserting a cryptographic tag into the headers. We construct this tag using a mechanism called public-key steganography. This means anyone can tag a connection using only publicly available information, but only the Telex service (using a private key) can recognize that a connection has been tagged.
As the connection travels over the Internet en route to the non-blacklisted site, it passes through routers at various ISPs in the core of the network. We envision that some of these ISPs would deploy equipment we call Telex stations. These devices hold a private key that lets them recognize tagged connections from Telex clients and decrypt these HTTPS connections. The stations then divert the connections to anticensorship services, such as proxy servers or Tor entry points, which clients can use to access blocked sites. This creates an encrypted tunnel between the Telex user and Telex station at the ISP, redirecting connections to any site on the Internet.
EDITED TO ADD (8/1): Another article.
EDITED TO ADD (8/13): Another article.
This isn’t good:
The hacker, whose March 15 attack was traced to an IP address in Iran, compromised a partner account at the respected certificate authority Comodo Group, which he used to request eight SSL certificates for six domains: mail.google.com, www.google.com, login.yahoo.com, login.skype.com, addons.mozilla.org and login.live.com.
The certificates would have allowed the attacker to craft fake pages that would have been accepted by browsers as the legitimate websites. The certificates would have been most useful as part of an attack that redirected traffic intended for Skype, Google and Yahoo to a machine under the attacker’s control. Such an attack can range from small-scale Wi-Fi spoofing at a coffee shop all the way to global hijacking of internet routes.
At a minimum, the attacker would then be able to steal login credentials from anyone who entered a username and password into the fake page, or perform a “man in the middle” attack to eavesdrop on the user’s session.
Fake certs for Google, Yahoo, and Skype? Wow.
This isn’t the first time Comodo has screwed up with certificates. The safest thing for us users to do would be to remove the Comodo root certificate from our browsers so that none of their certificates work, but we don’t have the capability to do that. The browser companies—Microsoft, Mozilla, Opera, etc.—could do that, but my guess is they won’t. The economic incentives don’t work properly. Comodo is likely to sue any browser company that takes this sort of action, and Comodo’s customers might as well. So it’s smarter for the browser companies to just ignore the issue and pass the problem to us users.
Sidebar photo of Bruce Schneier by Joe MacInnis.