Private key
Also called: secret key
Definition
A private key is a secret number that proves ownership of a crypto address and is used to sign transactions, so whoever holds it can spend the coins at that address.
How private key works
In most blockchains, a private key is a 256-bit number, often shown as 64 hexadecimal characters. From it, the wallet calculates a public key, and from the public key an address. This works in one direction only: you cannot work backwards from an address to the private key.
When you send crypto, your wallet uses the private key to create a digital signature. The network checks the signature against your public key and accepts the transaction without ever seeing the key itself.
Most people never handle raw private keys because wallets derive them from a seed phrase. Exporting a single private key is sometimes needed to import an account into another wallet, but it should be treated as carefully as the seed phrase.
Example
Picture a wallet with one Ethereum address holding 0.8 ETH. You export its private key to import the account into a second wallet app and paste the key into a notes app that syncs to the cloud. Months later the cloud account is compromised. The attacker finds the 64-character key, imports it, and sends the 0.8 ETH away in one transaction. Your seed phrase was never exposed, yet that address is lost.
Common mistakes
- Thinking a private key is safe to share because it is not the seed phrase.
- Pasting a private key into a website that claims to check your balance or fix a stuck transaction.
- Confusing the public address, which is safe to share, with the private key, which is not.
Learn and practise
FAQ
Can someone get my private key from my wallet address?
No. Deriving the private key from an address is computationally infeasible with current technology.
What is the difference between a private key and a public key?
The private key signs and must stay secret. The public key and the address derived from it are shared so others can send you funds and verify your signatures.