Monday, March 14, 2016

Letter to my MP about the Investigatory Powers Bill

I've just sent this email to my MP. Hopefully it will make a difference. I've asked for permission to post her reply.


Dear Ms Fernandes,

I am a resident of [redacted]. My address is [redacted]. I am writing to you a second time about the proposed Investigatory Powers Bill. I wrote to you about this on 5th November 2015 urging you to try to mitigate the worst aspects of this bill, and now I am writing to urge you to vote against this bill when it comes to Parliament.

I am deeply concerned about the powers that this bill would give to the Home Secretary. However in order to keep this email reasonably short I will concentrate on one particularly dangerous power.

If this bill becomes law then the Home Secretary would be able to order any "communications company" (the term could mean anyone involved in providing software or equipment that enables communication) to install any surveillance feature the Home Secretary wishes. The recipient of this order would be unable to appeal against it, and would be prevented from revealing the existence of the order. There is no sunset time on this gag clause: it will last as long as the Home Secretary and the security services wish to maintain it.

It is true that these orders will also have to be signed off by a judge, but that will only verify that the order complies with whatever procedures are in place at the time. Furthermore these judges will only ever hear one point of view on the reasonableness and proportionality of the orders, and this can only result in the erosion of these safeguards over time.

I want to illustrate the danger of this power to weaken security by showing how it would impact a common method of selecting encryption keys called Diffie-Hellman Key Exchange. This method is used by web browsers and email programs whenever they make a secure connection (e.g. to web addresses starting "https"). It is also used by "Virtual Private Networks" (VPNs) which are widely used by businesses to allow employees to work remotely, and I expect that Parliament has one to allow MPs to access their email. You may even be using it to read this.

I want to show that any attempt to intercept messages where Diffie-Hellman is used will greatly weaken it, and that this will worsen our security rather than improving it. I will show this by linking the NSA to the compromise of the Office of Personnel Management (OPM) in America last year.

I don't propose to explain the technical details of Diffie-Hellman. What it means is that two computers can exchange a few messages containing large random numbers, and at the end of this they will share a secret key without that key ever having been sent over the Internet.

Suppose that a communications company provides software that uses Diffie-Hellman, and receives an order from the Home Secretary that they must make the encrypted messages available to law enforcement and the intelligence agencies. What are they to do? They never see the secret keys, so they must do one of the following:

1: Modify the software to send a copy of the chosen key to someone. This is far less secure, and also very obvious. Anyone monitoring the packets sent by the programs will instantly see it.

2: Modify the software to make the keys or the encryption weak in a non-obvious way so that the UK intelligence agencies can determine what the key is. For instance, the random numbers might be made more predictable in a subtle way.

These are the only two ways in which the communications company can comply with the order.

We have seen what happens when Option 2 is chosen, because this was done to Juniper Networks firewall product [see ref 1 below]. Someone deliberately inserted "unauthorised code" which weakened the encryption used by this product in a very specific and deliberate way. There is no possibility that this was an accidental bug. The responsible party is widely believed to be the NSA, because secret briefings released by Edward Snowden made reference to the ability to intercept data sent via this product [ref 2], and it would be much easier for the NSA to infiltrate an American company than for anyone else to do it.

However there is something important that happens when software is updated: hackers (including foreign governments) scrutinize the updates to see what has changed. Normally they find that the old version of the software had a security hole which is now patched, so the patch flags up a way to attack computers that haven't been updated yet. But in this case when Juniper issued an update to their firewall software these hackers found the security hole in the *new* software.

Doing this kind of analysis in a systematic way for many security products is a very large job. Doing it in secret requires the resources of a government. So now not only could the NSA intercept communications sent via Juniper firewalls, but so could an unknown number of foreign governments. The Chinese were almost certainly one of them. Other nations known to have invested in  cyber-attack capabilities include the Russia, Israel and North Korea (although the last is probably not as capable yet).

Juniper products are widely used by the US Government. This is likely to have been one of the ways in which the Office of Personnel Management (OPM) was penetrated last year [ref 3]. The Chinese government is the prime suspect in this hack, through which the attackers have obtained copies of the security clearance applications of everyone who has ever worked for the US government.

So it seems that the NSA, by introducing a supposedly secret "back door" into a widely used product, cleared the way for the Chinese to obtain secret files on everyone who has ever worked for their government, including all of their legislators and everyone who works at the NSA. Nice job breaking it, Hero!

Now it is true that this is circumstantial; we have no hard evidence that the Juniper back door was inserted by the NSA, no hard evidence that the Chinese found it, and no hard evidence that this contributed to the OPM hack. But each of these is a big possibility. Even if the OPM hack didn't happen in exactly that way, deliberately weakening security makes events like this much more likely. If the Home Secretary orders a company to introduce weakened security, that fact will become apparent to anyone with the resources to dig for it. Once armed with that fact, they can attack through the same hole.

Furthermore, we would never find out when a disaster like the OPM hack happens under the regime described in the Investigatory Powers bill.  Suppose that, thanks to the weakened security ordered by the Home Secretary, secret government files are obtained by a hostile power, and the communications company executives are called before a Parliamentary Inquiry to account for their negligence; how can they defend themselves if they are legally prohibited from revealing their secret orders?

More generally, we will never be allowed to learn about the negative effects of these secret orders. It would embarrass those who issued them, and they are exactly the people who would have to give permission for publication. So if Parliament passes this bill it will never be allowed to learn about the problems it causes, and hence never be able to remedy the mistake.

I have focused on only one of the measures in the Investigatory Powers bill here, but there are many others in the bill that cause me great concern. To go through the whole bill in this level of detail would make this email far longer, and I know that you have many calls on your time. I can only ask you to believe that there are many similar issues. For these reasons I must urge you to vote against the bill when it reaches the House of Commons.

Yours sincerely,

Paul Johnson.




1 comment:

Anonymous said...

Thank you for taking the time to do this.