Every crypto balance is controlled by a secret, and whoever holds it controls the money. This article explains what a private key is, how it relates to your address, and what changes when a service keeps it for you.
Published September 30, 2026 · 3 min read
A private key is a secret that proves you are allowed to move crypto from a particular address. Think of it as the authorisation for every outgoing transfer: the blockchain does not ask who you are, only whether the transfer is authorised by the right key. That is why control of the key is, in practice, control of the funds. The coins themselves are not stored on your device; the key is what lets you act on them.
The public address is derived from the key and is what you give to someone who wants to send you crypto. It works like an account identifier for receiving: sharing it lets others pay you, but it does not let them spend. The private key stays secret because it is the part that authorises spending. One more practical point: each address belongs to one network, so when you share an address, make sure the sender uses the network it was issued for.
Blockchain transfers are irreversible, and that turns the key into a single point of failure. If someone gets hold of it, they can move the funds and the transfer cannot be undone. There is no support desk on the blockchain itself that can reverse a payment or restore access. Keep in mind the two ways this goes wrong:
In a custodial wallet the service holds the keys, so the user does not handle a private key or a seed phrase directly. You sign in, see your balance and send or receive through the app, while the key management happens on the service side. This removes the risk of losing a key yourself, but it means you rely on the service to protect it. In a wallet where you hold the key, the responsibility is entirely yours.
The choice comes down to who you would rather trust with the secret: yourself or a service. Holding your own key gives full control but no safety net if it is lost or exposed. A custodial wallet is simpler to use, and the protections depend on how the service is built. Nexus Pay, for example, is a wallet opened inside Telegram that offers an optional four-digit access code and keeps the main share of crypto funds in wallets without a permanent network connection.
| Option | Who holds the key | What you handle | Main risk |
|---|---|---|---|
| Custodial wallet | The service | Sign-in and app protections, not the key itself | Relying on the service to protect the keys |
| Wallet you control yourself | You | The private key or seed phrase | Losing or leaking the key, with no way to undo it |
Start with the basics: never share a private key or seed phrase with anyone, and treat any request for it as a red flag. Double-check the address and network before every transfer, because a transfer to the wrong address cannot be brought back. Turn on the protections your wallet offers, such as an access code. If you use a card linked to a wallet, features like freezing it in one tap, as in the Nexus Pay app, add a layer of control over spending.
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