Quote from: ranochigo on Today at 05:00:55 AM

You need to know the exact block hash to download, and having the block itself doesn't provide any form of security, which is why SPV wallets require at least the block headers.

In this post I wasn't looking for a replacement for a wallet, but for a block explorer - only with a little bit more privacy. If you use a block explorer, you also have to trust the provider of the service to deliver you the correct data. And of course the type of service I was thinking about should provide you all necessary data to check that, including blocks / block headers all the way down to the genesis block.

Quote from: ranochigo on Today at 05:00:55 AM

This means that you must know which are the blocks to download, which means you also have to trust someone to tell you the exact blocks and download those.

Ideally such a service should provide a web interface where you could enter the timeframe (e.g. you remember that you should have received a transaction between day X and day Y, so you would download all the blocks in-between). So the service provider doesn't have to know the exact blocks. Once the blocks are downloaded, you could then cut off the connection to the Internet and process the data offline via a JavaScript interface, e.g. searching for addresses and transactions. Or directly process it with command line tools or so.

The reason why this would be more privacy friendly than a SPV wallet is of course that on the SPV wallet the block data are on the server and you query addresses/transactions (which are then known by the server), while in the service I was thinking of, the server would only known the blocks you're requesting. Indeed technically it would be similar to BIP 157/158, only presented in another way and with more data analysis features.

I've looked a bit about privacy notices of some block explorers (five highest ranked on Google plus walletexplorer which I checked recently):

- httos://walletexplorer.com - shares all data with Chainalysis, basically no privacy
- https://blockstream.info - no separate privacy notice for the block explorer, according to Privacy Policy may share data with third parties, probably also bad privacy
- https://blockchain.com - Privacy Policy Section 7 says that they share data with a lot of different service providers including "providers of KYC or AML services". Probably bad privacy.
- https://btcscan.org - Privacy Policy (for all Redot services, no separate notice for block explorer) - mentions "compliance" and "research" companies as some of the parties they transmit data. Looks also bad for privacy.
- https://bitaps.com - Privacy policy doesn't mention that they transfer data to third parties, but also doesn't deny it. Quite unclear privacy.
- https://blockexplorer.one - Privacy Policy mentions GDPR (European data protection guideline), says that they don't transmit personal information to third parties, but they mention "Controllers" which could process data. Also a bit unclear.

May continue this list if there's interest.