formally verified?
In high-school maths, we are introduced to the idea of a
proof the word “proof” is etymologically related to the word “probe”. In a proof, we reason from first principles (aka
axioms), why a certain assertion (aka
theorem) holds true. Said differently, we
verify the theorem, and
proof represents the verification process.
The axioms and the proof need a language in which they are represented at a minimum, this language involves a syntax and a set of
proof rules governing that syntax. This mathematical rule-based verification is also called
formal verification, to distinguish it from the colloquial use of the word verification which may just involve human inspection.
Dear Legislator,
We are writing from the American Association for the Advancement of Science’s (AAAS) Center for Scientific Evidence in Public Issues and the U.S. Technology Policy Committee of the Association for Computing Machinery (USTPC) regarding Utah’s consideration of an expansion of insecure internet voting. AAAS, the world s largest multidisciplinary scientific society, and ACM, the world’s largest computing society, work to provide a voice for science on societal issues and promote the responsible use of science and technology in public policy.
Internet voting, referring primarily to the electronic return of a marked ballot via email, fax, web-based portal, or mobile apps, is not a secure solution for voting in Utah or elsewhere in any form, nor will it be in the foreseeable future. In April, we wrote to every governor, secretary of state, and state election director across the country detailing the scientific and technical risks of internet voting and urging offici
Pointers Are Complicated II, or: We need better language specs
just because two pointers point to the same address, does not mean they are equal in the sense that they can be used interchangeably.
This “extra information” that distinguishes different pointers to the same address is typically called
provenance.
This post is another attempt to convince you that provenance is “real”, by telling a cautionary tale of what can go wrong when provenance is not considered sufficiently carefully in an optimizing compiler.
The post is self-contained; I am not assuming that you have read the first one.
There is also a larger message here about how we could prevent such issues from coming up in the future by spending more effort on the specification of compiler IRs.