Greg Cordover

Thoughts & projects

Recent posts

Feb 18, 2020 — 5 minute read
Reverse Image SearchingChecking if files are identical is a trivial task. You could directly compare all their bytes or perhaps compute a hash of each file and compare those. Trying to compare the similarity of files’ content is an entirely more difficult task. What does similarity mean? How can a computer determine if two photos contain the same content after getting resized or compressed from being reposted on Reddit and Twitter? Due to the lossy nature of most image compression algorithms, you cannot compare the bytes of images to determine if they have the same content.…
Aug 1, 2017 — 5 minute read
Acetone Smoothing 3D Printed PartsA major inconvenience of 3D prints is trying to make them look better after they’re printed. Most consumer 3D printers work by melting and extruding filament into a thin line of plastic and moving the print head relative to a bed to create shapes. This process is known as FDM. While this process is relatively cheap and easy, the motion and layers often result in defects and often result in visible layers.…
Jan 8, 2016 — 3 minute read
Finding .git FoldersThe Git version control system stores all its data about current and past revisions of files in a hidden folder, called .git. By convention, one does not include information such as passwords in Git and instead should use environmental variables or other configuration methods. However, due to poor programming practices and the general laziness of developers in major software platforms, it is common for developers to include sensitive information. Most sane web servers will block access to hidden directories or files.…
Dec 6, 2015 — 7 minute read
BtrfsRetrieving data from a storage device is fairly simple, assuming an you know which track and sector the data is stored in. However, it is simply impossible for a person to remember all of these positions. A modern hard drive can store 8x10¹² individual bits of data! An Intro To Filesystems To solve the issue of remembering where files are on a disk, we have filesystems. One of the original filesystem is named FAT, or File Allocation Table.…
Aug 7, 2015 — 2 minute read
Availability of Short Twitter HandlesSomewhat recently, I wrote a post about signing up for Twitter accounts using their private API. I also talked about how there were endpoints for checking username availability. These endpoints have no rate limiting, which enables us to do many fun things. One such thing is checking over 2,000,000 handles to see if they were still available. On Twitter, short handles are a coveted thing. There are not many of them, and most have been taken.…
Jun 15, 2015 — 5 minute read
Registering Accounts Using the Twitter APITwitter uses an API for everything. Many people have seen the limitations of it, such as third party clients not being able to get favorites on Tweets or only 100,000 clients allowed per token. This API has many hidden methods and functions that most developers will never see, even though they are very easy to find. Official 1st party tokens have access to many methods you can find using an endpoint designed to show ratelimiting information.…
Aug 13, 2014 — 1 minute read
Twitter Visualizations, AgainA while back, I did some visualizations about Twitter’s grouping. Recently, I went back and ran some updates. This time, instead of calculating groups, I mapped out the connections between groups. This was the initial result, generated the same was as last time. This image doesn’t really look too much different. I then limited the connections to users who had just more than two mentions. Here’s where it got interesting! It seems that there’s some groups that just talked once or twice.…
Apr 11, 2014 — 3 minute read
Twitter VisualizationsTwitter is an interesting website, especially considering how basic its premise is: 140 character “status updates”. With these, you can talk about something briefly, share something interesting, or mention other users. I’m going to talk a bit about mentioning users here today. Twitter, from my experience, is extremely cliquey. There are certain groups of people who mostly mention or “subtweet” (referring to a user without actually mentioning them) each other very frequently, and only rarely mention someone outside of this group.…