Hardware wallets: Where are my cryptocurrencies actually stored?
Are my cryptocurrencies stored in the hardware wallet, or where exactly are they? This is a very good question because the answer defines what your wallet actually needs to protect.
Cryptocurrencies are so named because they are secured by cryptography. For this you need a set of digital keys, for example your (very secret) private key. With this key you can encrypt and digitally sign things.
Let’s take Bitcoin as an example (other cryptocurrencies work in a similar way). The entire Bitcoin network is kept up to date by a common data structure called the blockchain. It contains records of all transactions ever made and is publicly accessible online, so anyone can read it. When you receive some bitcoins, say 0.1 BTC, you see them in your bitcoin wallet, listed under a bitcoin address.
At the same time, the bitcoins are not actually stored in the wallet, they are just an entry in the public blockchain. What the wallet stores is your secret private key that belongs to that address. Since you control that private key, you can spend those Bitcoins again: that’s how “Bitcoin ownership” is defined. Anyone can see these bitcoins, but only you can spend it, so they are yours. But that also means that *anyone* with the right private key can spend those bitcoins. Therefore, it is very important to keep this key secret.