Use a hardware wallet to securely generate keys and sign transactions. Hardware wallet is meant for secure use of cryptocurrency, but it is not optimal for long term storage. It's important to buy devices only from trusted vendors, and to make sure they're not been tampered with (never buy them from a third party).
For long term storage, you need indestructible and physically secured backup of your keys. Basically, you just need to write down the 12 or 24 seed words generated by your hardware wallet and try to keep the words safe from destruction and theft. It's recommended to use a indestructible material such as steel for these, and then store or hide them safely. For more advanced security, seed words can be split in multiple parts using the SLIP39 seed format.
For long term storage, you need indestructible and physically secured backup of your keys. Basically, you just need to write down the 12 or 24 seed words generated by your hardware wallet and try to keep the words safe from destruction and theft. It's recommended to use a indestructible material such as steel for these, and then store or hide them safely. For more advanced security, seed words can be split in multiple parts using the SLIP39 seed format.
For hardware wallets, e.g.:
- https://coldcardwallet.com
- https://trezor.io
- https://www.ledger.com
For long term storage, e.g.:
- https://cryptosteel.com
- https://cryptotag.io/
- http://bitcoinseedbackup.com