Here are a bunch of blogs those I learnt and I liked.
Black Bauhinia: https://b6a.black/
This is the Capture-the-Flag team I founded with some Hongkongers on 2019. Contains a number of writeups on various CTF games.
Cocousin = Usin: https://klwu.co/
Cousin is a crypto guy in Black Bauhinia who is researching for his master of philosophy, and who can do math much better than I do. Apart from CTF writeups he also had some educational blog post on the math behind the crypto.
Blog by grhkm21: https://grhkm21.github.io/
Gareth is a young member of Black Bauhinia (10-ish years younger than me). I thought he is good at crypto but he is definitely more than that.
Ja5on’s blog: https://cuhkjason.github.io/
Jason is a member of Black Bauhinia. Being a red teamer, there will be red team tips apart from CTF writeups.
CryptoHack Blog: https://blog.cryptohack.org/
Apart from the awesome learning-by-doing style platform, CryptoHack has a blog talking about cryptographic challenges, and security incidents. One of which is the CryptoHackers recovering a partially redacted RSA private key.
Holocircuit’s blog: https://holocircuit.github.io/
The writeup of “Unofficial” (a challenge from 35C3 CTF) is really well-written. This is the first blog post I learnt on constructing lattices.
kylebot’s blog: https://blog.kylebot.net/
Although I don’t know binary exploitation at all, I found kylebot’s blog very interesting to read. I was motivated to start my blog shortly after he published his first blog post.
RBTree is one of the few CTF players who has a fanclub. There are a bunch of writeups on hard crypto challenges.