The Stellar App for the Ledger Nano S is the safest way to store your lumens. Using a hardware wallet keeps your private secure and always offline.
Anytime you enter your secret key when connected to the internet, particulary in a browser, you are exposed to the risk of a malicious hack similar to the Blackwallet attack - even if you are using a paper wallet.
The best way to avoid risk is to keep your secret key and sign transactions in an offline environment, and the easiest way to achieve this is a hardware wallet like the Ledger Nano S.
Your secret key never leaves the device, all transactions are signed on the device, and no transaction will go through unless you approve it on the hardware wallet. When approving a transaction on your hardware wallet, triple check to make sure the transaction is correct and no extra operations were snuck in.
Buy a Ledger Nano S here: https://www.ledgerwallet.com