Spectre

Hello there, $kas and $qubic fans, it's time for a little history lesson. Our story starts from an unknown time, in the Prussian city of Königsberg (now Kaliningrad, Russia), built on both sides of the Pregel river, which divided it into two land masses and two islands. Seven bridges were built for passage between the islands and mainlands, bridges that afforded a riddle: can a person take a walk, crossing each bridge exactly once, finishing where they started? It is unknown for how long this question has been asked, but it is known when it was answered and by whom: 1736, Leonhard Euler. Euler realized that we can completely forget the geometry of the town. The only information we need is a list of land masses, and the number of bridges between each two land masses. He encoded this information into what we call a graph -- a bunch of nodes connected by edges -- and quickly proved the first theorem in a field now known as graph theory: a graph can be traversed by a route starting and ending at the same point and passing through each edge exactly once if and only if each node touches an even number of edges. Solving the riddle of Königsberg's bridges in the negative. In the years to come, and already during Euler's life and through his work, math enthusiasts considered all sorts of graphs, including ones where edges can be only traversed in one direction, and it is impossible to take a walk on the graph that ends up where it started. In other words, a directed acyclic graph, or DAG for short. Albeit its name not yet in its final form, DAGs were used for parallel computation theory at least as early as 1972, as we can see in the seminal paper by Coffman and Graham [1]. Ideas of using DAGs in cryptocurrencies and DLTs started to emerge in the literature since the introduction of the GHOST protocol in 2013, but the idea was first thoroughly researched by Lewenberg-Sompolinsky-Zohar in the 2015 paper "Inclusive Block Chain Protocols" [2] The first proposal for a DAG based proof-of-work DLT is usually attributed to a 2015 hypothetical protocol called DagCoin. Proposed by Sergio Demian Lerner in 2015, DagCoin was the first to propose that users rather than miners are required to engage in proof-of-work to publish their own transactions. An idea that raised a lot of criticism. In general DagCoin was an interesting proposal, but it could not provide any tangible security, which is why it never left the drawing table. About a year later, a project called IOTA was the first to attempt building a production-grade DAG-based proof-of-work DLT, based on a protocol called Tangle invented by a guy you all heard of: first name Serguei, last name Popov. Tangle proposed to solve DagCoin's problems using a probabilistic method, but provided very little evidence that it is actually secure. Serguei and his fellow cofounders (three other guys, one of them, confusingly enough, called Sergey) ignored warnings from fellow researchers that the understanding of DAGs in consensus is yet lacking, and that the security of the Tangle protocol against double-spends seems unclear, and rushed to implement it. But as they tried to make the move from theory to practice while the theory is insufficient, reality knocked. Several attacks were demonstrated that in theory, could allow liveness and even double-spending attacks, forcing Iota to enrich their network with coordinators: centralized entities that resolve conflict. After years of attempting to fix Tangle and remove the coordinator requirement, Sergey left Iota to seek other ventures, while those remaining decided to scrape Tangle altogether, they started developing Tangle 2.0, a proof-of-stake reimagining of the application of DAGs to consensus. So if anyone ever tells you that this Sergey or the other "invented DAGs", be sure to audibly laugh in their face. Want to hear more about the history of DAGs in proof-of-work? Great! My current project is a video journey of the history of proof-of-work protocols, from Bitcoin to DAGknight. Be sure to sub to my youtube channel so that you don't miss it! youtube.com/@desheDives [1] mathweb.ucsd.edu/~ronspubs/7… [2] link.springer.com/chapter/10…