They use same cryptography tool that we use.
You don’t have any claim over your bitcoin. You need to read their terms and services. Customers comes at the last. The debt holder in the company have the senior claim in case of insolvency. You just own the iou.

Also I was talking about coinkite being the shitty company. The bitcoin only influencers are bunch of scammers. Don’t listen to them.

Self custody is simple. Don’t let these bitcoin only retards make you think that you need a complicated setup.

You buy a hardware, generate seeds, add passphrase and it’s done. Use reputable company that has a market value. Don’t waste your time in bitcoin only companies or open source software only type shit.

People who were using ledger/ trezor are still fine.