How PGP Works Under the Hood

  1. The plaintext is processed by a hashing algorithm such as MD5.
  2. The digest (this is the name of the output of a hashing function) is encrypted with Alice’s private key. When Bob will receive the message, he can decrypt the hash (Bob has Alice’s public key) and verify that the hash is correct. This is the signature of the message: we are sure that the message was send by Alice and that it was not modified by someone.
  3. The plaintex and the encrypted hash are now concatenated into a single message.
  4. This message is now compressed using the ZIP program.
  5. The compressed text is the input for the symmetric IDEA (International Data Encryption Algorithm). The IDEA algorithm uses a 128 bit key called Km. Km is randomly chosen.
  6. The 128 bit IDEA key (Km) is now encrypted with Bob’s public key.
  7. The encrypted key (6th step) is concatenated with the output of the IDEA algorithm (5th step).
  8. All this is converted in Base64.


An Introduction to Managing DNS

“DNS, or the domain name system, is an essential component of modern internet communication. It allows us to reference computers by names instead of IP addresses. In this series, we will cover the basic ideas behind DNS so that you feel comfortable working with it. Afterwards, we will walk through various ways that you can gain greater control over your domains and DNS resolution…”

Writing scientific articles like a native English speaker: top ten tips for Portuguese speakers

“Can you identify a single colleague who has not had a manuscript returned with the comment “needs to be reviewed by a native English speaker”? Many researchers receive this response even after translation or revision by an official translator or a native English-speaking coauthor. Over the past four years, while conducting my doctoral, and now my postdoctoral, work here in Brazil, I have been asked to both translate and help revise numerous manuscripts for my fellow Brazilian researchers. However, despite being a native English speaker and a researcher, I have found these tasks to be quite stressful at times. The truth is, just like it is one thing to write in Portuguese and another to write well in Portuguese, the same applies to writing well in English. Furthermore, not every native English speaker who writes well in English can write well for the scientific literature. Scientific English writing has its own style and rhythm, such as the use of passive voice. Passive voice is considered poor English in most forms of writing (news, novels, blogs, etc.) outside of science. The most recent version of Microsoft Office Word will even highlight passive voice as poor grammar and ask you if you want to rephrase. However, the use of passive voice is acceptable and even encouraged in some scientific writing…”

CentOS 7 with VirtualBox

To install VirtualBox Guest Additions on a CentOS 7 guest run this as root:

rpm -Uvh;
yum -y install dkms kernel-devel-$(uname -r) kernel-headers-$(uname -r);
mount -o loop VBoxGuestAdditions_4.3.14.iso /media/;

To install VirtualBox on a CentOS 7 host run these as root:

rpm -Uvh;
yum -y install dkms kernel-devel-$(uname -r) kernel-headers-$(uname -r);
yum -y localinstall;

An Illustrated Book of Bad Arguments

“This book is aimed at newcomers to the field of logical reasoning, particularly those who, to borrow a phrase from Pascal, are so made that they understand best through visuals. I have selected a small set of common errors in reasoning and visualized them using memorable illustrations that are supplemented with lots of examples. The hope is that the reader will learn from these pages some of the most common pitfalls in arguments and be able to identify and avoid them in practice…”