Bitcoin blocksize increase discussion – summary and analysis of proposals.

by Albert Szmigielski Introduction Currently Bitcoin blocks are limited to 1 MB. This limit implies a certain number of transactions per time frame. Bitcoin blocks are found on average every 10 minutes, therefore on average we can expect 7 transactions per second. In order to compete with established companies, Bitcoin must scale up and therefore increase the blocksize to allow more transactions per time frame. Increasing the blocksize would require a hard fork. Anytime major changes are required to the Bitcoin protocol different interest groups raise their concerns and lobby for their interest. Proposals There were four proposals for increasing the blocksize put forward. They can be found in BIPs 100 through 103, and BIPs 105, 106, the unofficial 248,

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Double-spending attack in BitcoinXT

by Albert Szmigielski BitcoinXT implements a double-spending countermeasure that forwards the first double-spend attempt to other nodes. In order to mount a double-spend attack we must make sure that the vendor does not learn about the double-spend transactions As with any other double-spend attack it starts with forming two transactions: TXV which is used to pay the vendor, and TXD which sends the same inputs to an address controlled by the attacker. The goal is to have TXD confirmed in the blockchain, while having TXV accepted by the vendor in exchange for goods/services. Assumptions and requirements: Able to connect directly to the vendor Able to send TXV to the vendor Able to send TXD to the Bitcoin Network Prevent the

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