~elly/blog 2025-09-17T00:00:00Z elly urn:uuid:58e1c539-4056-4502-9445-29d725e4df97 urn:uuid:caf3d982-2bdd-6f67-198d-6b0f4da99597 The libraries I built for Advent of Code Advent of Code: Libraries 2025-09-17T00:00:00Z urn:uuid:b0423f4c-840a-c6fb-4a75-48246e19e250 My experiences solving every Advent of Code challenge released so far Advent of Code: 500 Stars 2025-09-01T00:00:00Z urn:uuid:d23088e0-e9f3-60a2-ab15-12ef7c4ae175 How to choose a random subset of a large set efficiently Reservoir sampling 2025-05-17T00:00:00Z urn:uuid:2c43eb19-7261-4a41-9225-4dc421f9a1b7 How do X.509 certificates actually work, and what's actually inside them? X.509 Certificates 2024-03-08T00:00:00Z urn:uuid:65f72cdc-49ee-44d3-977b-6a55380ca74f An introduction to the fossil vcs, and some comparison to git Fossil 2023-10-20T00:00:00Z urn:uuid:da506b94-5c8d-4c7e-8ca5-d2061c5893ce A cryptographic technique to create constrainable auth tokens Macaroon MAC Chaining 2023-04-07T00:00:00Z urn:uuid:17970ff6-5f9e-4cdc-8740-dfada20a04b7 A neat technique for building parsers out of smaller parsers Parser Combinators 2023-02-20T00:00:00Z urn:uuid:fa0742fc-78c5-441f-aead-76a937055caf A quick tour through the source of rogue(1), one of the classic Unix games Rogue Source Tour 2022-12-30T00:00:00Z urn:uuid:a0587479-5c8e-46e6-933d-0a4def188776 A technique for shipping binaries which are provably derived from specific source trees Binary Transparency 2022-12-28T00:00:00Z urn:uuid:f7ebd45d-24a6-4c50-bd86-b9d703e1bc80 Experiences doing Advent of Code 2022 in Fennel, a tiny Lisp that compiles to Lua Fennel for Advent 2022-12-25T00:00:00Z urn:uuid:c56810ef-16f4-46a8-96fd-8a7c2d5a60d0 My experiences creating and publishing my first package for Alpine Linux Packaging for Alpine 2022-10-31T00:00:00Z urn:uuid:1036d6de-674b-4008-b094-d95da0b6cd14 My experiences using Alpine Linux on an 11th gen Framework laptop Alpine on Framework 2022-10-20T00:00:00Z urn:uuid:d487d730-dc30-4010-9aca-d00762b0b08c An introduction to the lambda calculus, given as a Scheme program Lambda Calculus 2022-10-09T00:00:00Z urn:uuid:7573b7e2-a564-4301-8e25-fd261a5421a6 Why do some libc structs have prefixes on all their names? Struct Member Naming History 2022-09-30T00:00:00Z urn:uuid:2f258466-e6b6-4f3d-b4a9-68c75dc59901 A rewrite of the historic GPM in C, slightly touching on differences between C and CPL General Purpose Macrogenerator 2022-09-15T00:00:00Z urn:uuid:810a455a-efb4-41dc-b75e-24ed3fd2fa0d Trying out the Hare programming language Hare First Impressions 2022-09-14T00:00:00Z urn:uuid:7ca3e7cd-cf54-4581-a482-e653bde5e9b2 Some thoughts on protecting your most important data, and how I do it Doing It Right: Passwords, Keys, and Backups 2022-09-01T00:00:00Z urn:uuid:966fe25c-2bbb-45e4-bebb-7a14e88338e6 A worked example of how some types of JIT compilation work, in C Just-In-Time Compilation 2022-05-05T00:00:00Z urn:uuid:648f3c52-0a80-41cf-82ec-2fcd6fa50b24 Some design notes on how to structure an IRC client with an eye towards persistent presence IRC Client Design Thoughts 2022-04-18T00:00:00Z urn:uuid:6a0469a7-7e8f-455e-9217-237dcf7b84cd An overview of email anonymization tools and attacks against them Cipherpunks, Mixmaster, and Mixminion: Anonymous Email 2022-02-09T00:00:00Z urn:uuid:b6a4e893-0b42-4429-9bdc-a041d2fd986c A review of "A Psalm For The Wild-Built" by Becky Chambers Book Review: A Psalm For The Wild-Built 2022-02-01T00:00:00Z urn:uuid:147fb97a-48c5-4a8a-a4da-21f2bc01b15d An amd64 assembly of the core of the chacha20 stream cipher The ChaCha20 Cipher Core 2022-01-26T00:00:00Z urn:uuid:a02d26cf-2049-4103-b5cb-3082225d4bb8 The world's simplest image format! The PPM Image Format 2022-01-24T00:00:00Z urn:uuid:35ffbaaa-542c-4d67-aeff-4f3df7889f0c How I make backups of my systems, 2022 edition Backups 2022-01-18T00:00:00Z urn:uuid:377668d4-5f53-40b6-9c7b-5c49144db8c9 How self-extracting shell tarballs work and why they exist Shellballs and self-extractors 2022-01-13T00:00:00Z urn:uuid:b6c57535-a880-4faa-be8f-5236d8e611b3 A historical overview of the m4(1) macro language m4 2022-01-05T00:00:00Z urn:uuid:73bee03c-6d42-4ef7-802f-ea81c10ff377 History and design of the tar(1) file format Tarballs 2022-01-03T00:00:00Z urn:uuid:ed550a85-83e9-43a3-8aff-96543d8ef925 Where exactly did autotools come from, and what were the people who created it thinking? Whence Autotools? 2022-01-02T00:00:00Z urn:uuid:2df192ce-3463-4e15-9951-72e39285da26 In cryptography, what are constant-time operations and why do they matter? Constant-Time Operations 2022-01-01T00:00:00Z urn:uuid:eaaf9aab-46f3-468f-b74c-43257a18e7ff An algorithm for doing precedence-aware parsing of mathematical expressions into a sequence of stack ops in a single pass The Shunting-Yard Algorithm 2021-12-31T00:00:00Z urn:uuid:cc236173-19de-448b-b0ba-ef912e609ce0 A fast algorithm for finding substring matches, implemented in C The Boyer-Moore String Search Algorithm 2021-12-30T00:00:00Z urn:uuid:8f7f77a8-e66f-4d9b-b87d-9d02ebb6e456 How instruction encoding and decoding works in hardware and software Virtual Machines, Part 1: Instruction Encoding 2021-12-29T00:00:00Z urn:uuid:c477f106-2c98-45f5-a51d-14495ac36716 How length-extension attacks work against Merkle-Damgard hash functions Length Extension Attacks 2021-12-28T00:00:00Z urn:uuid:c58cc95f-7349-47b4-b80d-c11e01e22583 What virtual machines are, how they work, and a worked example of one in C. Virtual Machines, Part 0 2021-12-24T00:00:00Z urn:uuid:b26c34b7-958c-4216-a3b5-ade15a23e52a How the subdirectories in my home directory are laid out and why My Homedir Layout 2021-10-06T00:00:00Z urn:uuid:da8efd0e-173e-459a-bbf9-fa601f64ea9b Some notes from getting my Pinebook Pro set up Pinebook 2021-06-01T00:00:00Z urn:uuid:2e8cc582-67ec-4aee-aac5-8e716078f947 A data structure (a tree of hashes) to allow for efficient validation of parts of a huge data set. Merkle Trees 2020-09-12T00:00:00Z urn:uuid:4a8bf736-67e9-4cda-af03-77f350ea4f8b A way to use trees of hashes to produce a simple, post-quantum signature scheme Lamport Signatures 2020-09-12T00:00:00Z urn:uuid:ddc052a7-b834-4b42-8445-d76698c0958a A data structure for handling buffered messages being fanned out to many clients Broadcast Buffers 2020-09-10T00:00:00Z urn:uuid:136f5f04-03bd-4dc3-aadf-4564811eeb76 What makes protocols "boring", and why is boring-ness desirable? Boring Protocols 2020-09-07T00:00:00Z urn:uuid:51661f3a-c40f-4417-8d5c-8380afb01005 A way to register members of a set (modules, etc) at program startup time in C++ without needing to fill out a big table at compile time The C++ static constructor registration trick 2019-11-16T00:00:00Z urn:uuid:0a802f02-d4df-442d-83c4-64fa1360db61 A cool data structure for distributed programming Linda Tuple Spaces 2019-11-15T00:00:00Z urn:uuid:534622fc-f60d-4e69-a41d-198d01ad77b6 How to use /bin/ed! Using The ed(1) Text Editor 2015-10-03T00:00:00Z urn:uuid:e84f5be7-d8cb-4320-a787-99cd175cd047 Just a bit of life advice stolen from Ann Landers. Rules For Getting Along With Others 2015-09-29T00:00:00Z urn:uuid:e6cb57aa-5e41-4ce6-8ab5-8a61206ae6ae What the main components of a rudimentary Unix userland are and how to write them in C. Writing a Unix Userland 2015-05-18T00:00:00Z