James Lovejoy, recent MEng MIT grad and former graduate researcher at the MIT Digital Currency Initiative, joins the show to talk about his masters thesis and associated project focusing on detecting double-spends in proof of work cryptocurrencies. Previously, little data was collected in a systematic way to detect double-spends and reorganizations across many cryptocurrencies. James' project sheds light on previously unknown security properties of PoW. In this episode:  How James came to work on Vertcoin Why James thinks ASIC resistance is valuable James' blockchain monitoring project and why it matters Why reorgs are challenging to detect Why investigating the economic damage of reorgs is difficult How James noticed a 51% attack in progress on Vertcoin and intervened to save Bittrex money – and how this can be replicated Why understanding Nicehash is critical to detecting and dealing with 51% attacks James' critiques of dominant theoretical models of PoW security How James found reorgs and counterattacks happening on BTG in real time Why exchange processes like KYC might actually help protect blockchains from reorgs How permissionless trading and leverage makes certain blockchains more vulnerable to attacks Rules of thumb for confirmation requirements for exchanges The issue with calling coins "Nicehash-able" – and why it's likely a lowball How exchanges can proactively mitigate the risk of 51% attacks and what they should be targeting How BTG developers finally defeated deep reorgs Whether James is confident in the long-term prospects of PoW Whether James still believes in GPU mining Content referenced in this episode James Lovejoy, An Empirical Analysis of Chain Reorganizations and Double-Spend Attacks on Proof-of-Work Cryptocurrencies Raphael Auer, Beyond the doomsday economics of “proof-of work” in cryptocurrencies Eric Budish, The Economic Limits of Bitcoin and the Blockchain Hasu, Prestwich, and Curtis, A model for Bitcoin's security and the declining block subsidy Carlsten, Kalodner, Narayanan, Weinberg, On the Instability of Bitcoin Without the Block Reward Moroz, Aronoff, Narula, Parkes, Double-Spend Counterattacks: Threat of Retaliation in Proof-of-Work Systems Judmayer et al, Pay-To-Win: Cheap, Crowdfundable, Cross-chain Incentive Manipulation Attacks on Cryptocurrencies Liao and Katz, Incentivizing Blockchain Forks via Whale Transactions James Lovejoy and David Vorick, ASICs and cryptocurrencies: benefits and drawbacks  [debate] Nic Carter, It's the settlement assurances, stupid [blog] Elaine Ou, Cryptocurrency Deals can Always be Erased, for a Price [article]