In computer science, recursion is a method of solving a problem where the solution depends on solutions to smaller instances of the same problem. For example, a factorial can be calculated recursively by multiplying a number by all the numbers below it. Recursion can be used to solve problems in many different areas, such as … Read more


The XKeyscore program is a database management system used by the United States National Security Agency (NSA) to search and analyze global Internet data. According to leaked documents, XKeyscore is the NSA’s “widest-reaching” system for collecting Internet data. The XKeyscore program collects and stores data on a variety of Internet activities, including emails, chat messages, … Read more

Circular logging

Circular logging is a method of logging in which the log files are overwritten in a circular fashion. This means that the oldest log file is overwritten when the disk is full. This can be useful in situations where the log files are not needed for long-term analysis and where disk space is limited. Should … Read more

Let’s Encrypt

Let’s Encrypt is a free, automated, and open certificate authority (CA), run by the Internet Security Research Group (ISRG). Let’s Encrypt issues certificates for Transport Layer Security (TLS) encryption at no charge. This is an important service because it allows website operators to secure their sites with HTTPS without having to pay for a certificate. … Read more