Computer and network security, reverse engineering, security vulnerability research and exploitation, high-performance computing, GPGPU, assembly optimization, free and open source software, Unix kernels internals, decentralized cryptocurrencies (Bitcoin), entrepreneurship, angel investing, etc.
In 2011 Andrés Ruzo began studying the Shanay-timpishka, a boiling river in the Amazon . It is described as “a natural feature: a non-volcanic, geothermal feature flowing at anomalously high rates”, see this National Geographic interview . The non-volcanic claim was interesting to me… Apparently groundwater finds its way in deep-rooted faults in the Earth’s crust and is heated according to the…
Shipping companies like FedEx or UPS sometimes determine the shipping rate by calculating the dimensional weight , or dim weight, of the package. For example, FedEx instructs their American audience to calculate the size in cubic inches and then to divide by 139 . Others may use a divisor of 166 or 194. The result is the dim weight in pounds. 139, 166 and 194 are not obvious at first sight—the…
I made a Linux kernel patch to support ECC memory on AMD Ryzen 5000 APUs (codename Cezanne.) It applies cleanly and works on kernel versions 5.13 through the latest (5.16-rc2). Step-by-step patching in Debian 12 (bookworm) Origin story Step-by-step patching in Debian 12 (bookworm) The instructions below for Debian 12 (bookworm) are minimally intrusive. They install only one modified kernel module…
When I buy a laptop, the first thing I do is netboot into a PXE Linux environment and make a full raw disk image backup of the pre-installed Windows OS. I pipe dd if=/dev/sda or dd if=/dev/nvme0n1 into lz4 (much faster than gzip ) and write the image on a fileserver. No matter how large the disk is, the image usually shrinks down to 20-30 GB because, well, there are usually only 20-30 GB of files…
A semi-popular Twitter thread by @boriquagato argues that stay-at-home orders are ineffective at reducing mortality in the US: “ there is just no evidence that this incredibly expensive and harmful policy has any effect at all. ” This is, of course, preposterous. @boriquagato attempted to rank US states by cumulative deaths per capita, and observed how the ranking changed over ~4 weeks. I will…
Estimating the case fatality ratio (CFR) of the 2019 novel coronavirus is crucial to inform policy makers and help them make the best decisions. As of 7 February 2020 in mainland China there are 31 161 confirmed cases, 637 deaths, 1 540 recoveries. So some claim the case fatality ratio is 637/31161 = 2%. But this is as naïve as claiming the recovery ratio is 1540/31161 = 5% thus that the fatality…
In this post I will reverse engineer the Costco Android app to find out how the digital membership card works, and how to generate the time-based token encoded in its QR code. I reimplemented it in plain HTML/JS. As a result the card can be cloned to any number of devices, bypassing the app’s security mechanism that attempted to tie the card to only one device. 2022-10-11 Three years later, this…
I reviewed the following two research reports published by analysts at Morgan Stanley on the subject of Bitcoin electricity usage: Bitcoin ASIC production substantiates electricity use; points to coming jump , by James E Faucette et al., January 3, 2018 Bitcoin demand > EV demand? , by Nicholas J Ashworth et al., January 10, 2018 The first report estimates current electricity consumption at 2500…
In the context of the Bitcoin scaling debate, small blockers believe that if the block size limit is doubled, running a fully validating Bitcoin node will become expensive and only well-funded corporations will be able to run nodes, hence increasing centralization. However facts and data disprove this narrative. Here is a fact: despite blocks currently averaging 1 MB it is possible to run a full…
March 2017 was a significant moment for Bitcoin: the average block size bumped into the 1MB limit, stunting the growth of the transaction rate ever since. Many arguments are made about how to increase capacity (changing the limit, developing off-chain solutions, etc.) However very rarely are discussions centered around facts and data such as estimating the impact of the stunted growth so far and…