Stories About Secrets

It is alleged – in the Sunday Times yesterday – that Russian and Chinese intelligence agents have cracked encrypted data in the Snowden files, thus compromising the cover of  British and American agents who have had to be moved to ensure continuing  operational security. No one has been harmed.

Glenn Greenwald, the journalist who co-ordinated the release of the Snowden files, has written an article here claiming that the Sunday Times piece is wrong. I haven’t read the Sunday Times story. It is behind a paywall and I have vowed for many years that the Murdoch family will never get another brass farthing of my money.

No independent person can have any way of knowing which side to believe. So, for the sake of argument, I will assume that the Sunday Times is right – that it’s not just acting as a mouthpiece for ASS propaganda. (ASS abbreviates for Allied Security Services, meaning essentially the UK and US intelligence services – CIA, NSA, GCHQ, MI6 and MI5 – and their champions and apologists in government and media.)

I assume that The Snowden Files, the data dump taken by Snowden consisted of:

  • A lot of cleartext procedural information about the extent and nature of data surveillance by the ASS (this is mostly what has already been revealed); and
  • Some cyphertext files containing ASS operational information (this is what is alleged to have been compromised, and which Snowden promised would not be revealed).

Procedural information describes how the ASS operate. It is information which might understandably have been available to a security contractor such as Snowden and would generally be accessible to everyone in the organisation. This is why it was held in cleartext on ASS internal servers and Snowden could download it all.

Operational information would include things such as agents’ identities, their location, their cover, and reports they may have submitted. It is highly sensitive and even within any branch of the ASS would be available only on a need-to-know basis. It should be encrypted with a long symmetric key,  which itself would be encrypted using an asymmetric algorithm to the key pairs assigned only to those need-to-knows.

  •  This encryption should be secure enough to allow the cyphertext to be transmitted over public networks.
  • If any of the key material to access this data had been available to Snowden, it represents a scandalous lapse in ASS internal security.

If the Sunday Times story is true, then either:

  •  Russian and Chinese intelligence have broken ASS cryptography; or
  • ASS internal security was already compromised.

ASS cryptography is broken?

Modern cyphers are vulnerable to various attacks. The simplest is a brute-force attack, and it has been demonstrated to work for short key-lengths around 128 bits using a network of computers running in parallel over several hours. Increasing the key length by one bit doubles the effort for a brute-force attack. It is a trivial problem for a large enough quantum computer but  no one is known to have built one sufficiently capable yet.  ASS should have been using long keys – at least 256 bits. A network of computers that could crack 128-bit encryption in a second would take about ten followed by twenty zeroes times the age of the universe to crack 256-bit encryption. So a brute force attack is unlikely.
More complex attacks use weaknesses in the encryption algorithm or software. Usually this involves a lack of randomness. Symmetric keys are long random numbers; if they are not truly random, they are much easier to break.
Most successful attacks use the human vector: procedural errors, or getting someone who does know a key to disclose it. (Despite Alan Turing’s genius and the new computers, it was Nazi procedural errors that let Bletchley Park into Enigma).

Most likely explanation

The Sunday Times story is partially true. ASS have assumed  that the operational information has been compromised, because the Russians and Chinese have had access to the cyphertext, and they have made the necessary operational adjustments to protect their agents.  Which they would do anyway, because you should always assume that your enemy can access your cyphertext.

ASS are very keen that the mass surveillance revealed by Snowden should continue and they want the legislative framework right. In both countries – the US and the UK – they are fighting political battles to give them the legal and political powers to do so. They want to discredit Snowden and show him as a traitor rather than a patriot, and the planted story is intended to achieve this.

However, if it shows anything, it shows first that ASS internal security procedures are not as good as they should be. And for lots of reasons, that should worry us, regardless of our position on Snowden.

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