Jun 9, 2016
Databending is a type of glitch art wherein image files are intentionally corrupted in order to produce an aesthetic effect. Traditionally, these effects are produced by manually manipulating the compressed data in an image file. As a result, this is a trial-and-error process; often, edits will result in the file being completely corrupted and unopenable.
Someone recently asked me whether I knew why databending different types of image files produces different effects – and particularly, why PNG glitches are the most interesting. I didn’t know the answer, but the question inspired me to do a little research (mostly reading the Wikipedia articles about the compression techniques used in different image formats). I discovered that most compression techniques are not all that different. Most of them just employ some kind of run-length encoding or dictionary encoding, and then a prefix-free coding step. The subtle differences between the compression algorithms could not explain the wildly different effects we observed (except for in JPEGs, perhaps, since the compression is done in the frequency domain). However, PNG used a pre-filtering step which made it stand out.
Apr 28, 2016
As you probably know, PEM is a base64-encoded format with human-readable headers, so you can kind of figure out what you’re looking at if you open it in a text editor.
For example, let’s look at an RSA public key:
-----BEGIN PUBLIC KEY----- MIICIjANBgkqhkiG9w0BAQEFAAOCAg8AMIICCgKCAgEA4YFgwNrEkMdynjtDsM0q b+Hedk8p4pySfxakYTfSQPEyGxxnQGcVMV2ZEjPR4nZeqJrtNTlixhK2YWqunE6I KopVDq3WvtPKweNEeZ8B2lA2I8FFrpZSjI/Tosq8/MbTd/Y/C4Q8Qcz78MF/NH17 /E82K3ca9/LM2b4KGTEIhsLUff7OGrJM7lPcQZN3EOdUeQnzT9uTh8Z9oFqChfJP pLwwSebfrRB7VMXjeKHZmubSO5pULHLdZLbkgLSmnhbgBjO6apG0tkYyOeWd6L8F MzA21WkXJdANrr1s/yv5zS9hx1q9jSM8Me9QA2/iaAbgem7VwQ2YlPiXEvUq48oB VsKXMpHQ6A2cUygs+PiSFuUzNjTIebWFTWmKKuoRx0O2m63fAZJaT2aJA4G0HqdJ ZQ2Aqr4Acs1+28IhLxUbMAlHJ4N2XPnE2WpQYbtUR4zZMXU+bVIToXuqHCLo4pf/ qEIK/xzr/S8WdvMvRVSOtVIIQwyaMDUxsnnKozYSVHvzYsxQo3b3VD5OOqmg1mx1 +Z/PLFViLkBjo+ZMkl5dFbsgYyHmkn/uvCV19IpjkdDNfFgdrOlSdNTnlGU7su5L L31k/IwSvD0PR0egxiv8HhegaYwqgujVylB0gntyBsrVVHfE3Wr2+aJlR3YmrdCZ lsAiSbnFxgGtfB6INHepFdkCAwEAAQ== -----END PUBLIC KEY----- We can see that we have a public key just from the header.
Mar 28, 2016
Let’s Encrypt is old news by now. It launched back in December, so it has been giving away free DV certificates for nearly four months now. Being a TA for a Computer Security course, it’s about time that I actually tried it out.
Prologue
Let’s Encrypt is a free certificate authority. They grant TLS certificates that you can use to secure your webserver. They are Domain Validated (DV) certificates, which means they will verify that you control the domain name you are trying to certify.
Feb 4, 2016
Introduction DES (Data Encryption Standard) is an old-school block cipher which has been around since the 1970s. It only uses a 56-bit key, which is undeniably too short for use in the modern day. Between the realization that DES is weak in the late 90s and the invention of AES in the early 2000’s, Triple-DES had a brief time to shine.
Triple-DES is just what it sounds like: you run the DES algorithm three times.
Jan 9, 2016
I first heard about Twilio a long, long time ago. As Google Voice faded out of relevance, it took the lead in the mobile-communication-as-a-service market. However, I had never had the chance (or inclination) to play around with its API until today.
About 12 hours after we landed back in the US from our holiday in Mexico, Lynsey departed once again – this time to the Plant and Animal Genome conference (PAG) in San Diego. She asked me to supply her with pictures of our cats for the duration of her trip. I told her I would send her a cat pic every hour, on the hour.
I didn’t realize what I had gotten myself into until I had already deposited $20 into a new Twilio account and spent 2 hours coding away… Though my goal was just to send some photos of cats, I had developed a pretty general application that lets you build a queue of MMSes to be disseminated at a constant rate.
Dec 2, 2015
Authentication is the process by which a system determines whether a particular user is allowed to access it. There are three widely agreed-upon methods to authenticate a user:
- Something you have.
- Something you know.
- Something you are.
When you use your key to unlock your front door, you are authenticating yourself using something you have. In information security, passwords are the most popular method of authentication; they are something you know. Authentication by something you are (i.e., biometrics) has historically been only a niche practice, but in recent years it has caught on in the realm of consumer electronics.
When Apple announced Touch ID in late 2013, security experts immediately voiced their concern. The authentication mechanism was quickly compromised, and there is still very little that Apple can do about it. Why, you ask? Because fingerprints are inherently insecure.
Sep 2, 2015
I often feel inclined to start new projects to avoid working on old ones. In a particularly ironic display of procrastination, I have written a productivity-oriented application in order to avoid actual productivity. The app is called InSTiL, and its goal is to make it easy to log how much time you spend working on various projects. The source is available on Github, and the Readme provides a succinct overview of InSTiL’s functionality.
Feb 1, 2015
The inotify API allows you to monitor a file or directory for various events such as file creation, modification, and deletion. It is part of the Linux kernel and the glibc userspace library, however its C API can be cumbersome to use in a C++ application. A C++ binding of inotify does exist, but it still requires the application developer to write an unsightly wait-and-handle loop. My goal for this project was to create an asynchronous event-driven API through which filesystem events can be processed.
Jan 31, 2015
My current project is porting RIOT OS to the EK-TM4C1294XL evaluation board. RIOT is an embedded operating system aimed at the Internet of Things, developed primarily by Free University of Berlin. The EK-TM4C1294XL is a pretty powerful board, featuring an ARM Cortex M4 MCU and built-in Ethernet MAC. So far, I have implemented only the most basic support for the CPU - just timers and UART. However, I’m currently working on the Ethernet drivers (almost done) and my next focus will be drivers for an XBee add-in.
Jul 24, 2014
Dynamic DNS, or DDNS, is a type of DNS configuration which allows hosts with dynamic IP addresses to automatically update their DNS records. Often users will rely on services such as DynDNS or No-IP to manage this type of setup, but it is actually relatively easy to run your own DDNS server. Of course, this requires that you have your own domain name and access to at least one host with a static IP (to use as the DNS server).