Tag Archives: reference

Big Ball of Mud

Posted on by

These patterns explore the forces that encourage the emergence of a BIG BALL OF MUD, and the undeniable effectiveness of this approach to software architecture. What are the people who build them doing right? If more high-minded architectural approaches are to compete, we must understand what the forces that lead to a BIG BALL OF MUD are, and examine alternative ways to resolve them.

A number of additional patterns emerge out of the BIG BALL OF MUD. We discuss them in turn. Two principal questions underlie these patterns: Why are so many existing systems architecturally undistinguished, and what can we do to improve them?

Source: Big Ball of Mud

NSA in P/poly: The Power of Precomputation

Posted on by

Diffie-Hellman is the thing where Alice and Bob first agree on a huge prime number p and a number g, then Alice picks a secret a and sends Bob ga (mod p), and Bob picks a secret b and sends Alice gb (mod p), and then Alice and Bob can both compute (ga)b=(gb)a=gab (mod p), but an eavesdropper who’s listening in only knows p, g, ga (mod p), and gb (mod p), and one can plausibly conjecture that it’s hard from those things alone to get gab (mod p). So then Alice and Bob share a secret unknown to the eavesdropper, which they didn’t before, and they can use that secret to start doing cryptography.

Source: Shtetl-Optimized » Blog Archive » NSA in P/poly: The Power of Precomputation

secmodel_securelevel

Posted on by

The securelevel mechanism is intended to allow protecting the persistence of code and data on the system, or a subset thereof, from modification, even by the super-user by providing convenient means of “locking down” a system to a degree suited to its environment.

Source: NetBSD 6.1.5 – man page for secmodel_securelevel (netbsd section 9) – Unix & Linux Commands

Highly secure mode may seem Draconian, but is intended as a last line of defence should the super-user account be compromised. Its effects preclude circumvention of file flags by direct modification of a raw disk device, or erasure of a file system by means of newfs(8). Further, it can limit the potential damage of a compromised “firewall” by prohibiting the modification of packet filter rules. Preventing the system clock from being set backwards aids in post-mortem analysis and helps ensure the integrity of logs. Precision timekeeping is not affected because the clock may still be slowed.

Top Open-Source Static Site Generators

Posted on by

The typical CMS driven website works by building each page on-demand, fetching content from a database and running it through a template engine. This means each page is assembled from templates and content on each request to the server.

For most sites this is completely unnecessary overhead and only ads complexity, performance problems and security issues. After all, by far the most websites only change when the content authors or their design team makes changes.

A Static Site Generator takes a different approach and generate all the pages of the website once when there’s actually changes to the site. This means there’s no moving parts in the deployed website. Caching gets much easier, performance goes up and static sites are far more secure.

via Top Open-Source Static Site Generators – StaticGen.

An Introduction to Semiconductor Physics, Technology, and Industry

Posted on by

The simplest place to start is the materials. Silicon is incredibly important as a material in the industry because it’s a semiconductor. Of course, the name is self-explanatory, but there’s more to it. The key here is the band structure. Band structure refers to the “bands” of energy levels that form due to the sheer number of orbital states that can be occupied in molecules. Those that understand how electron orbitals work will point out that each energy level is discrete, but due to the sheer number of orbital configurations, a seemingly continuous distribution of energy can be seen. However, relatively large gaps still exist; known as a band gap, these are an energy state that an electron cannot occupy.

via AnandTech | An Introduction to Semiconductor Physics, Technology, and Industry – Print View.

And on and on it goes.  This is a great writeup for understanding how integrated circuits work.