A safe way to remove objectionable content from the blockchain

The email discusses a novel approach to addressing the challenge of managing objectionable content on the Bitcoin blockchain without compromising the integrity and functionality of the technology. The sender proposes two key changes, one at the consensus level and another at the client level, aiming to enable node operators to filter and remove content they find disagreeable post-mining, while still maintaining the benefits of running a full node.

The motivation behind these proposals stems from the immutable nature of blockchain technology, where altering any piece of data within a block would change its hash and, by extension, compromise the integrity of the entire chain. This presents a significant challenge when it comes to removing or changing objectionable content—defined subjectively by each user—since the blockchain's design does not allow for such modifications without consequences.

The solution offered involves a sophisticated method of maintaining data integrity through hashing, even when parts of the data stream are removed. The first idea centers on understanding the internal state of a hashing algorithm at two points (A and B) within the data processing sequence. By knowing these states, it is possible to compute the final hash of the data despite the absence of information between points A and B. This process allows for the deletion or alteration of the intervening data without affecting the overall integrity of the blockchain, assuming secure access to the internal states S(A) and S(B) can be obtained and shared among nodes.

The second idea builds on the trust inherent in the blockchain network, proposing that the only reliable source for obtaining S(A) and S(B) is the blockchain itself. By embedding these states directly into the blockchain through mining and verification processes, nodes can confidently delete objectionable data between S1 and S2, relying on the network to maintain ledger accuracy and integrity. This mechanism also facilitates the sharing of modified transactions among nodes that choose to exclude certain content, ensuring the continued functionality and reliability of the network despite individual preferences regarding content.

In conclusion, the email presents these concepts as an initial step towards fostering a dialogue on how to reconcile the need for content moderation with the foundational principles of blockchain technology. It invites further discussion and collaboration on refining and potentially implementing these ideas, emphasizing openness to different platforms and forums for continuing this conversation.