In response to my earlier post on why 0! should be 1, several people replied that 0! = 1 because an empty product is 1. You can define the factorial of an integer n as the product of all positive numbers less than or equal to n. There are no positive integers less than or equal […]
Last spring I wrote a post on spherical trigonometry, the study of triangles drawn on a sphere (e.g. the surface of the Earth). Mel Hagen left a comment on that post a few days ago saying I am revisiting Spherical Trig after 30 years by going back over some of my books that I have […]
I’ve never written a line of Ruby, but I find Ruby on Rails fascinating. From all reports, the Rails framework lets you develop a website much faster than you could using other tools, provided you can live with its limitations. Rails emphasizes consistency and simplicity, deliberately leaving out support for some contingencies. I listened to […]
The canonical example of the normal distribution given in textbooks is human heights. Measure the heights of a large sample of adult men and the numbers will follow a normal (Gaussian) distribution. The heights of women also follow a normal distribution. What textbooks never discuss is why heights should be normally distributed. Why should heights […]
On its surface, Unicode is simple. It’s a replacement for ASCII to make room for more characters. Joel Spolsky assures us that it’s not that hard. But then how did Jukka Korpela have enough to say to fill his 678-page book Unicode Explained? Why is the Unicode standard 1472 printed pages? It’s hard to say anything pithy about […]
AlphaFold 2, FourCastNet and CorrDiff are exciting. AI-driven autonomous labs are going to be a big deal [1]. Science codes now use AI and machine learning to make scientific discoveries on the world’s most powerful computers [2]. It’s common practice for scientists to ask questions about the validity, reliability and accuracy of the mathematical and […]
A SWIFT-BIC number identifies a bank, not a particular bank account. The BIC part stands for Bank Identifier Code. I had to look up the structure of SWIFT-BIC codes recently, and here it is: Four letters to identify the bank Two letters to identify the country Two letters or digits to identify the location Optionally, […]
Two of the first things you learn in cryptography are that simple substitution ciphers are very easy to break, and that security by obscurity is a bad idea. This post will revisit both of these ideas. Security depends on your threat model. If the threat you want to protect against is a human reading your […]
In 2018, three researchers from the US Census Bureau published a paper entitled “Understanding Database Reconstruction Attacks on Public Data.” [1] The article showed that private data on many individuals could be reverse engineered from public data. As I wrote about a few days ago, census blocks are at the bottom of the US Census […]
Table of Contents 1. General data privacy questions 1.1. What’s wrong with the nothing-to-hide argument? 1.2. Does removing names make data deidentified? 2. HIPAA, Expert Determination, and Safe Harbor 2.1. Is there more to Safe Harbor than 18 rules? 2.2. Does Safe Harbor really protect privacy? 2.3. Why does Safe Harbor remove dates of service? […]
