A couple of days ago I was introduced to a new data structure I did not know before. It’s called a skip list. It’s a sorted linked list, where the nodes are linked at different levels, forming increasingly sparse chains, each of which skips more nodes, and therefore is faster to traverse, allowing search algorithms to hop over parts of the list when searching. That’s why they’re called skip lists.

The concept was shown to me during a job interview. They briefly introduced me to the concept of skip lists using an image. It is said that an image is worth a thousand words, and in this case the assertion holds:

After I finished the interview I went on to find out more about skip lists, and I was amazed on how I did not stumbled upon them before. Immediately my instinct was to try out the algorithm I came up with during my interview, and when I saw it worked, I ended up writing a whole new SortedMap subclass in Java, implemented with skip lists.

It is surprisingly amazing how easy it is to write the routines for all the basic operations on skip lists, like adding, updating, removing and querying on them, specially when you see it described as a probabilistic data structure, which you have to admit that looks scary at first glance.

Performance

Well some guys did something very similar. They took an iPad for a ride in a Zero-G parabolic flight, similar to the well-known NASA’s Vomit Comet. Can you guess what happened to the iPad? Surprise!

Maybe not as serious as the problem that Jim Lovell and his crewmates had on Apollo 13, but a problem indeed. I was really not surprised at all, since I expected no more, but it’s nice to see that someone actually gave it a try.

You gotta love Jim Parsons on this scene. For me it’s the funniest scene on the whole series so far. It makes me laugh every time I see it. I hope you enjoy it too.

Update: Unfortunately the Youtube video above is not embeddable, so it cannot be played within this site Simply click on it to be given the option to open it on Youtube instead.

Luckily there are lots of different choices of password managers, softwares that will help you keep a secure database of all this information, sometimes even in a way that they help you collect your passwords as you use them in your browser, autofill login forms, and even generate new random passwords for you.

This is all great, but I am not convinced. Random passwords generated and filled into forms, all done by a software tool? I end up not really knowing my passwords. What if the tool ever fails, or its database gets corrupted? What if my hard drive melts and after the fix I get a clean install with no passwords database? I also do not like the idea of passwords being stored digitally, not even encrypted.

So I ended up with a small password managing system that I designed myself. With it you can still use a conventional password manager, but in a slightly different way.

Grab some passwords…

I have a small set of around nine or ten different passwords that I use for all the services and accounts I have access to. These passwords range across all the spectrum of difficulty and strength.

Then I distribute this set of passwords more or less evenly across the whole spectrum of services and accounts that I have access to. I use strong passwords for the most precious and important services; the dumb passwords for unimportant stuff, like all the garbage sites that require membership for even the dumbest thing; and I leave the medium-range passwords for most of the average-but-important services that most people, including me, use these days.

…but store keywords instead

For this password system to work you really ought to remember the actual passwords yourself. The password managing system is mostly just to remember what passwords are used for what access, not to remember the actual passwords. You can keep these associations between user accounts and passwords stored in several different ways, so it’s pretty easy to use, not needing any specific software. You can use an actual password manager, or you can use an Excel spreadsheet or a simple text file, just as I do. The medium is really up to you.

There are a couple of rules when setting up this associations list

1. Do not store the actual passwords in the associations, just small bits of text that loosely resemble, reminds you, or have any obscure-for-anybody-else relation to the password. It can be a small bit of the password itself, perhaps a bit tweaked, reversed, or with some phonetical changes. Or it can be something textually unrelated to the password, but having some association with it that only you can devise.
2. Each password should have at least two different keywords that you’ll associate with it, and not just one. This ensures that if somebody ever gets access to this associations, it won’t be easy to determine what services use the same password.

An example

I’ll give you an example with my own passwords and keywords (not really). We’ll work with a set of six passwords with various levels of strength. Notice in the stronger cases the use of L33T 5PEAK and other tweaks.

As you can see, most keywords by itself do not reveal the password, not even remotely. And even if someone ever guesses the relation, the password itself is usually more than the part that links to the keyword, with the further complication of tweaks in the spelling, the use leetspeak and similar encodings, etc.

But remember that you do not really write down the table above. What you really do is write down a list of services and accounts, and the keyword that associates a password with it, instead of the actual password. During the creation of this list below is when you really think about keywords associated to your passwords.

You can now store this table in whatever format you prefer, and take whatever measures to not loose it. You should also store it in a secure location, but in a way that you can access it whenever you need to lookup for something, or to modify it. Dropbox and Evernote are good choices. In Dropbox you can store it in a password protected file as well, if you think you can use some extra security.

But…

Sure this system has some drawbacks. For instance, some people might argue that some password managers also fill out login forms for you when integrated to the web browser. So even if you do use one of these password managers to store just the keywords and not the actual passwords, then the autofill-login-form feature becomes useless. But hey, who access content on the Internet via web browsers anymore?

What tools or systems do you use to manage your ever-increasing list of passwords and user accounts?

I’ve been flirting around with this idea for a while without actually taking some action, and a recent set of blog posts about these subjects have prompted me to start doing something about it. These and other posts, mostly from a couple of blogs I started reading not so long ago, are giving me ideas on how to break the inertia and start doing instead of just thinking and planning. They’ve shown me some of the obstacles in my way, mostly related to things you can change, instead of things that are out of our control. I spend a lot of time blaming my stagnation on external conditions, when there are lots of things under my own control that I can start changing to be more productive, things like the Internet and e-mail habits, lack of time scheduling, etc.

It’s not an easy task though. It requires discipline, because you can be told what to do and still do nothing, but in that case you have no excuse. This way, you’re at least more conscious that you need to take some responsibility for your life, that you can’t get always away with blaming everything on external conditions out of your control.

By the way, the two blogs I mention are Freestyle Mind and Michael Hyatt‘s personal blog. Not all of what they post is about this subject, and I do not agree with all of what they post about it, but they are great for a start, so I’ll be playing around with some of the ideas and adapt them to my own environment.

Do you know any other useful blogs or sources of information that can help me and others in changing habits, being more productive, being a doer instead of just a planner?

It allows you to select what version of Rails (and Ruby) to browse, and the most awesome part is that you can download a compressed package to browse it offline locally in your own computer. It includes Rails 3 beta and Ruby 1.9.x as well.

Meanwhile I am enjoying a similar experience. Somebody noticed out there that there are many of us with an iPad already (kind of). The iPad nano has been around for a couple of years now but with another name. And I recently got one and I am delighted with it. Why going crazy about the new one when you can have the nano version which fits in your pocket, has a camera and makes phone calls too!

iPad nano

Now seriously, after using the iPhone for some days I understand why people are crazy to experiment with its big but younger brother. Touch screens are seriously redefining how we interact with computers and from a developer standpoint it’s amazing the whole new set of possibilities that arise. And it’s not only touch screens and multi-touch, but also the ability to make a program adapt to different orientations of the device, to be able to access hardware services like a compass, accelerometer, GPS, etc.

My new MacBook seen from behind

I finally ended this mac envy that has been consuming me for the last few months. Being a Ruby on Rails developer for some time now, all those screencasts and tutorials always based in MacOS X and Textmate have had an effect on me. Although it seems that I’ll be playing mostly with xcode instead of Textmate for some time, but it’s sexy to have Textmate just an inch away in case I need it.

PS: For the couple of friends of mine that already had a Mac, my envy was not malicious.

That’s me. And that’s what this blog will talk about, mostly. Experiences, tips, opinions –about software development and software or technology in general. I might go off topic from time to time though. Whatever comes to my mind.