I assume it's the same as when it was mentioned in 2019
"A 32-bit hash prefix like "ba7816bf" would represent the first eight characters of a 256-bit, 64-character SHA256 digest of a full URL.
Before it loads a requested website, Safari, like other browsers that implement a safe browsing lookup system, will hash the URL of the website to be visited and compare its hash prefix to the received hash segments of malicious sites."
"A 32-bit hash prefix like "ba7816bf" would represent the first eight characters of a 256-bit, 64-character SHA256 digest of a full URL."
Is this done for 'privacy'?
Pretty thinly veiled attempt, because they could easily create hashes for every url their crawlers come across, and do some statistical wizardry to try to find out which of the 1000 urls with that prefix you visited. Right?
Of course it's done for privacy. If Google created hashes for every single URL it crawled, the hash prefixes that are downloaded by clients would be enormously large, wasting multi gigabytes for on-device storage of these hash prefixes.
"A 32-bit hash prefix like "ba7816bf" would represent the first eight characters of a 256-bit, 64-character SHA256 digest of a full URL.
Before it loads a requested website, Safari, like other browsers that implement a safe browsing lookup system, will hash the URL of the website to be visited and compare its hash prefix to the received hash segments of malicious sites."
https://news.ycombinator.com/item?id=21254166
https://www.theregister.com/2019/10/14/apple_china_tencent/
https://developers.google.com/safe-browsing/v4/urls-hashing#...