Sometimes I'll spend hours searching books and online to figure out how to do something that's ends up only being a couple lines of code. So if I can help anyone, why not?

A Crash Course in Cryptography Part II – Symmetric Ciphers

This entry is part 2 of 2 in the series A Crash Course in Cryptography

Today we will be delving into symmetric ciphers. I will remind you that this course is an introductory one. That means we won’t be digging deeply into the specifics. Yes, we will talk a little about the algorithms and their applications, however it will mostly be abstract. For instance we will talk about what a hash is, but not pick out the mathematical differences between SHA-1 and MD5.

What is a symmetric cipher? Symmetric, secret, private key, these are all synonyms for a specific class of cryptography. Symmetric ciphers all have one thing in common, a secret. That’s it. The encryption is only as strong as this secret and who knows it. As the old saying goes, “Three can keep a secret if two of them are dead.” That said, let’s get one with it and find out what implications that has.
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Using Encrypted PayPal Buttons (EWP) and IPN

If you want to accept PayPal payments on your site you have a variety of options. What I consider to be the ideal solution is a pairing of their IPN service with encrypted buttons. This allows your customers/clients to pay you securely without having to host an SSL cert on your site. Using encrypted buttons we can dynamically generate the amount values without having to worry about them being tampered with. Sure you could always verify the amount later, but why bother when there’s an easily solution around that, plus who really needs the hassle? This guide will walk you step-by-step from the question of “how?” to setting up a sophisticated payment solution.
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The Power of 802.11

The goal of this paper is to educate the reader on the power of 802.11 wireless LANs. The power to which I refer is literal power, measured in wattage. This paper will guide you through understanding how that power is expressed and explain decibel mathematics. You will learn how to add power or “gain” either passively or actively as well as how power can be lost. The various types of antennae available and their uses will be also addressed. Lastly, we will close by discussing FCC regulations governing the maximum EIRP (a term you will learn through reading) and the special requirement imposed by the IEEE.
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Just Enough SQL

Today we will be talking about SQL. I’m sure you all have many questions, not the lease of which is probably along the lines of: “What is SQL?” You are also probably curious as to how knowing it can help you in some way. Will it let me control the universe? Rest assured, all of your questions will be answered in today’s tutorial. Not counting the ones that are not answer of course. Today’s course is aimed at giving you just enough information to work w/ a database. We will not be talking about advanced topics like relational databases, left/right joins, nested statements or even what a primary key is.
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A Guide to Reading Perl

This tutorial is intended as a reference for experienced programmers. It gives a short descriptions of some of the main aspects of perl one is likely to find in the script they just downloaded. This is not a tutorial on writing perl scripts.
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