Wallets, keys & addresses

A “wallet” doesn’t hold coins — the coins live on the blockchain. A wallet holds your keys. Understanding what a wallet really manages, and the different ways to keep it, is the practical heart of self-custody.

The seed phrase — your master key

When you create a wallet, it generates a seed phrase: usually 12 or 24 ordinary words, like “ripple lunar cactus …”. Those words ARE your money. From them, your wallet mathematically derives every private key, public key and address you’ll ever use. Anyone with the words has full control; anyone without them can’t touch a satoshi. Write them down, store them safely — this is the one thing you must never lose and never reveal.

Addresses

An address is what you give someone to receive Bitcoin — derived from a public key (via the elliptic-curve maths from the Cryptography section). It’s safe to share. Best practice is to use a fresh address for each payment: your wallet generates unlimited addresses from the same seed, and rotating them improves privacy, since it’s harder to link your transactions together.

Hot vs cold — where the keys live

🔥 Hot wallet

Keys on an internet-connected device — a phone or browser app. Convenient for spending small, everyday amounts, but exposed to malware and hacks. Treat it like the cash in your pocket: handy, but don’t keep your life savings in it.

❄️ Cold wallet

Keys kept offline, never touching an internet-connected computer. Far safer from remote attackers. This is where you store savings you rarely move — the vault, not the pocket.

🔒 Hardware wallet

A small purpose-built device that stores your keys and signs transactions internally — the keys never leave it, even when plugged into an infected computer. The most popular way to do cold storage well, balancing strong security with usability.

📄 Paper wallet

Keys (or a seed) written or printed on paper and stored physically. Completely offline, but fragile — fire, water, loss, or fading ink can destroy it, and spending from it safely takes care. Largely superseded by hardware wallets and steel seed backups.

Multisig — no single point of failure

A multisignature (“multisig”) wallet requires several keys to authorise a transaction — say, 2 of 3. No single key can move the funds alone. Keep the three keys in three different places (home, work, a relative’s house), and a thief who finds one gets nothing, while losing one doesn’t lock you out. It’s how individuals, families and companies secure serious amounts, removing the “one key = one point of failure” risk.

The mental model. A small hot wallet for spending, a hardware (cold) wallet for savings, and for larger holdings a multisig so no single mishap is fatal. Your seed phrase is the master backup behind all of it. Get these habits right and you are your own bank — which is exactly the freedom, and the responsibility, Bitcoin offers.

That responsibility comes with rules of the road. The final lesson is the security hygiene that keeps self-custody from going wrong.

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