---
layout: post
date: 2018-04-04 01:24:00 +0800
title: 'Random thoughts on the controversy regarding the Facebook page "名校Secrets"'
---
[Context: Hong Kong Facebook users, age 13-<~30]

In an era where everyone is talking about blockchains, I'm surprised no-one has proposed using a blockchain-based bulletin board as an alternative to the said page.

It would work a bit like BitMessage (though my last usage of it was about 5-6 years ago, and no pun intended), but each message is a signed cleartext broadcast instead of an encrypted message, and perhaps with the added features of quoting and/or replying to previous messages, and/or adding likes/dislikes, similar in feature to PTT.

There are two potential problems (assuming no 51% attacks), the first being a lack of (monetary) incentive for block-writers. I don't suppose "SchoolCoin" would attract any monetary value, so such a BBS would have to rely solely on donated processing power (kind of like Tor relays). The second problem is spam/scam. Client-side spam filters can be implemented; note however that filter rule writers may be trying to censor posts.

Implementing an effective like/dislike / upvote/downvote system may not be straightforward. A spammer or a censor with sufficient resources can easily abuse it for their benefit. Potential mitigation: IP-address-based scoring system which reduces the importance of votes if many votes originated from the same IP address? Tor/open proxies may be used to bypass this, and reducing vote importance simply based on IP address being an exit node is being unfriendly for privacy-minded users or users suffering from large-scale internet censorship. So perhaps we can weigh votes based on past contributions, or even based on the received votes of past posts (though probably more computationally expensive to calculate). A sigmoid function may be a good choice for weighing, so that enthusiastic users won't be given too much importance. An alternative is to have a logarithmic upper bound.