- Where metamask store privatekey? are they stored locally or remote?
- How does metamask protect my privatekey? I assume that they are somehow encrypted by the seed phrase?
- How does metamask restore/import my wallet (using the seed phrase)? if the privatekey store locally then how does it work when using new computer? if it is stored remote, what measure are taken to secure and keep the data availble?
- should I back up the private key from the metamask wallet, or does the seed phrase is enough to secure the coins at any circumstance?
Your private key is stored in your browser.
Metamask ask you for a password to encrypt the private key.
No it's stored locally.
Always back up your private key. It's better to store your "mnemonic phrase" as they are human readable. A naked private key is hard to copy, and any error (a character change) can be lethal for your back up because you can't see the error.
I login to metamask from a different PC with the seed phrase only and verified that the private key are the same, thus metamask back the private key on remote server (probably encrypted by the seed phrase)
BUT reddit users complains that sometime the import process fails therefore it is important to backup the private key as well!