Glossary
Private key: the secret that controls your crypto
Your crypto is not stored in your wallet. The wallet stores keys, and the private key is the one that matters most.
A private key is a randomly generated secret code that lets you authorise transactions for the crypto it controls. Whoever holds it can move that crypto, and if you lose it without a backup, access is gone for good.
Quick answer
A private key is a randomly generated passcode that lets you authorise transactions for your crypto [1]. It works like a signature only you can make. If you lose it, you permanently lose access; if someone copies it, they can move your crypto.
Key points
- A private key authorises transactions; the matching public key only lets others verify them and send you crypto [1].
- Bitcoin's design treats ownership as a chain of digital signatures made with each owner's key [3].
- A wallet holding 0.05 BTC holds 5,000,000 satoshi, and one copied key is enough to move all of it (calculated).
On this page
What does private key mean?#
The SEC describes a private key as a randomly generated alphanumeric passcode that allows you to authorise transactions for a crypto asset [1]. It comes in a pair with a public key. The public key is used to verify transactions and receive crypto, and it cannot be used to authorise transactions or to reach the private key [1].
That is why people say a wallet holds keys, not coins. The coins are recorded on a blockchain; the key is what lets you move them. Three other things are easy to confuse with it, so the table sets them side by side.
| Secret | What it does | Safe to share? | If you lose it |
|---|---|---|---|
| Private key | Authorises transfers of the crypto it controls | Never | Access is lost permanently, unless a backup can rebuild it |
| Public key | Lets others verify your transactions and send you crypto | Yes, it cannot authorise transfers | No direct risk: it cannot authorise transfers |
| Seed phrase | Restores the wallet and the keys it generates | Never | No way to rebuild the wallet if the keys are also lost |
| Exchange password | Logs you in to an account where the company holds the keys | Never | The company can usually reset it |
Private key, public key and seed phrase as described in the SEC custody bulletin [1]; seed phrase restoration under BIP-39 [2]. The public-key and password rows describe the usual set-up; check your own wallet or exchange.
How does a private key prove you own crypto?#
The Bitcoin whitepaper defines an electronic coin as a chain of digital signatures [3]. Each owner transfers the coin by digitally signing a hash of the previous transaction and the public key of the next owner, and anyone receiving it can check those signatures to verify the chain of ownership [3]. The key that makes each signature is the owner's private key.
So on a blockchain, owning crypto means being able to produce a valid signature. There is no name on the account and no help desk. The whitepaper also aims for transactions that are computationally impractical to reverse [3], which is why a signature made by the wrong person still counts.
What happens if you lose or leak a private key?#
Losing it is permanent. The SEC warns that if you lose your private key, you permanently lose access to the crypto in that wallet [1]. A seed phrase can restore the wallet if you lose it or its private key [1], which is why that backup needs the same protection as the key itself. Our guide to seed phrase vs private key explains how the two connect.
Leaking it is just as bad. One of the SEC's tips is never to share your private keys or seed phrases [1]. Scammers ask for them through fake support chats and fake websites; see crypto scams for how those requests look.
If an exchange holds your crypto, you usually never see a private key at all: with third-party custody, the provider holds your crypto for you [1]. That moves the key risk to the company. Our page on custodial vs non custodial wallet weighs the two set-ups.
Frequently asked questions#
Can I share my public key?
Yes. The public key is used to receive crypto and verify transactions, and the SEC notes it cannot be used to authorise transactions or to reach the private key [1].
Can a lost private key be recovered?
Does an exchange account have a private key?
The crypto in it is controlled by keys, but with third-party custody the provider holds them for you [1]. You log in with a password and two-factor authentication instead; see 2fa for crypto accounts.
The bottom line#
A private key is the signature behind every transfer of your crypto. Keep it secret, keep a safe backup through your seed phrase, and never type it into a site or chat you reached from a message. Read the risk disclosure before buying any crypto.
Sources
Education only. This page is not investment, tax or legal advice. Trading and crypto can lose you money. See our risk disclosure.
