| man-in-the-middle Information I am not sure most people understand how SSL works and how man-in-the-middle attacks work.
SSL requires some information to be exchanged before an encrypted session is established. Your browser and the server you are connecting to negotiate encryption protocols, key hashes, etc. before actually starting an encrypted session.
Since the ISP is between you and the server you are connecting to they can record all of the negotiated information that is used before the encrypted session is enabled. Once this information is recorded they can fully decrypt and intercept all traffic that is sent over the encrypted link. When key changes happen they get the updated key as well since they are intercepting all traffic.
The only protection against this type of man-in-middle attack is to pre-distribute encryption keys and authentication information. This prevents the ISP (Or any other man-in-the-middle from being able to intercept the initial seeds of the encrypted link. Without this information the ISP cannot easily decrypt the encrypted session to inspect the contents for filtering/content/throttling/etc.
This is why you see banks distributing USB flash drives with password randomizers to their corporate customers. This is one way to prevent man-in-the-middle attacks. The USB flash drives that our accounting department are provided by the bank also have a time component to them. They must press a button on the USB key which displays an 8 digit alphanumeric combination that is valid for five minutes. They then insert the USB key which loads cryptographic software onto the computer. They then connect to the bank's website and are prompted for the 8 digit key. Since the bank distributed the USB key, the protocol negotiation setting up the cryptographic keys does not happen and initial keys are determined by using the time sensitive 8 digit key from the USB flash drive.
Since it is impractical to do this for Bittorrent and many other types of encrypted sessions over the public internet, the security of any encrypted session using industry standard protocols, regardless of cipher strength or complexity, is nowhere near assured. This has been known to security professionals for many, many years. It is also why many companies pre-distribute digital certificates, smart cards, etc. Most corporate firewalls configured by security professionals will be setup this way so that man-in-the-middle attacks are not possible.
The enigma machine that the Germans used during WWII worked in a similar way. It was never cracked until an actual machine was captured by the enemy. The Germans had code books that contained single use codes for each machine. Headquarters had copies for decryption purposes. This custom code changed the cipher each time the machine was used. This made it impossible for the allies to decrypt the communication without having physical access to a machine and possibly a code book.
The only protections you have are privacy laws which make third party attacks like this illegal without a warrant. These laws are only effective when you can PROVE the ISP is violating them. Since most bittorrent traffic is illegal content, the user cannot complain without admitting to the transfer of pirated material. Legitimate traffic that has been intercepted, decrypted and modified/read could expose the ISP to legal ramifications. The chances of someone actually prosecuting the ISP for this type of infraction are quite low and they know it.
I could foresee offshore companies setting up a business model around pre-distributing security keys. This would be very similar to the way digital certificates work, but instead of proving identity they would offer, for a fee, preconfigured security keys that would take out the man-in-the-middle attack. All parties would need to use this system for the network to be secure. You would really need to trust this third party to not divulge your private keys. This could be a lucrative market for companies in Antigua. Nothing would prevent media companies and ISPs from also joining this network. Group distribution of encrypted material would never be secure unless you could control who authenticates the clients allowed to join |
