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Thursday, 2 October 2014

The Foundation (Part I)


I wrote this to try once again to explain what is the nature of the problem that one would have in verifying the integrity of any  software toolchain, whether it is aimed ultimately at the production of other software, or of hardware.

 https://github.com/IanANGrant/red-october/blob/master/judgemnt.pdf

This three page text is ostensively about verifying the integrity of a communications link operating over an un-trusted transport layer, but a compiler is really a type of communications channel.

I am sure everyone still reading this has wondered about the possibilities of using universal programming languages (universal in the Church-Turing sense) as communications protocols. For example, one could establish a point-to-point connection by writing a program which, when run, output two more programs: one which, when run, outputs a decoding pad for the next mesage one would transmit over that channel, and the other the decoder which prints the message text together with another program, which was the encoder for returning an
acknowledgement. Both endpoints would do this, and so the programs/messages would be exchanged, with each one encoding the text of the other.  Then these programs could include decisions not only about the encoding of data, choice of one-time pads, etc. but perhaps also the routes of messages, sending different parts via different trusted routes over similar channels etc. etc. The variations are endless, and limited only by the ingenuity of the programmers communicating over those channels.

And really, I sorely pity anyone charged with organising any kind of surveillance of a group of people who enjoy that sort of game. Cracking "the code" would be practically impossible, because there need never be any fixed concrete representation whatsoever of the fundamental encoding as it is transmitted over the transport medium: all of the knowledge about the current and future encodings can be sent over the previous "incarnations" of that and/or another
channel, and the encoding of channels thereby made non-deterministic:
this means that there could never be in principle, any mechanical
process whatsoever which could decode more than a few parts of any
of those messages. After this brief success, the poor would-be spy
would be right back at square one.

What I try to explain here is the essential distinction between what I call actual knowledge, as opposed to mere represented knowledge, such as a password, or an SSL certificate, or the documentation for some file format appearing on a web page. The distinction is that only in the case of actual knowledge does one know how and why one knows.

The motivation is the idea that by using actual rather than represented knowledge, it is possible to construct such a trustworthy system in practice. But there's a catch! The catch is that this will only work for an organisation whose motives and governance are completely open and transparent. This is because the technique relies upon mutual trust, which is something that cannot exist without openness and transparency. Bad guys just won't get it! To understand why (in case it is not immediately obvious to you, that is) you will need to read (or at least think carefully about) about how error-detection would work in such a system.

The text consists of a title page with the abstract, and two full pages. So it should be an easy read. I earlier sent out a nine page document entitled GNU Thunder, in which I attempted to describe what I consider to be essentially the same idea, but with the emphasis on compilers and interpreters, rather than communications. The Thunder text was a concrete suggestion for an implementation. This text however is more abstract. But these two documents could be considered to be complementary in two different senses.

I hope everyone enjoys this, and that it stimulates some interesting thoughts, and subsequent discussion, and that those thoughts are all good, and the discussion open and transparent. That way we could save ourselves an awful lot of really hairy metaprogramming!

Please feel free to copy either text and/or this message and pass it around. Neither of these two texts are copyright, and the more people that see them the better. Bad guys in particular need to know about this much more than the good ones do.

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