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What Is a Private Key? Definition & Why You Must Protect It
A private key is a secret number that proves you own the crypto at an address and lets you authorize spending it — whoever has the key controls the coins.
Key takeaways
- Your private key is what actually controls your crypto; the wallet app is just a convenient way to use it.
- It mathematically produces your public address, but the address can't be reversed back into the key.
- Anyone who gets your key can spend your coins, and there is no way to undo it.
- Never type your key into a website, message or 'support' chat.
How a private key works
A private key is a very large random number. From it, a one-way mathematical process produces a public key, and from that, the public address people send coins to. You can share the address freely because going backwards — from address to key — is computationally infeasible.
To spend, your wallet uses the private key to create a digital signature for a specific transaction. The network checks the signature against the public key; if it matches, the spend is valid. The key itself never has to be revealed, which is why a wallet can sign for you without exposing it.
Why protecting it matters
Blockchains have no account recovery and no fraud department. If someone else obtains your private key, they can sign transactions exactly as you would, and confirmed transactions can't be reversed. Equally, if *you* lose the only copy of the key, the coins at that address can never be spent by anyone.
Keys, recovery information and wallets
Most wallets don't ask you to handle raw keys day to day. They store the key encrypted on your device and give you recovery information so you can restore access on a new device. Some wallets use a single master phrase for every coin; others give each coin its own independently recoverable key. Either way, the recovery information is as powerful as the key itself and should be treated the same way.
Common mistakes
- Typing recovery information into any site or app other than the wallet you trust
- Storing the only copy in a screenshot, email or cloud note
- Believing someone who says support needs your key to "fix" a problem — no legitimate support ever will
Example
You create a Litecoin wallet. The app generates a private key on your phone and shows an address for receiving. You can post that address publicly; only the private key — kept encrypted on your device — can spend what arrives there.
Put it into practice
Every coin gets its own recoverable key
In Scrypt Wallet each coin has its own private key, generated and encrypted on your device, and you can recover access using your individual coin keys — no single master phrase tying everything together. Support will never ask you for a key.
Create a free wallet Get Scrypt for AndroidFrequently asked questions
What's the difference between a private key and a public address?
The address is what you share to receive coins. The private key is the secret that authorizes spending from it. The address is derived from the key, but the key can't be derived from the address.
What happens if I lose my private key?
If you also have no recovery information, the coins at that address can't be moved by anyone, permanently. That's why backing up recovery information before adding funds is essential.
Does Scrypt Wallet use one key for every coin?
No. Each coin in Scrypt Wallet has its own independently recoverable private key, generated and encrypted on your device.
Written by the Scrypt Wallet team · Updated 2026-09-29. General education, not financial, tax or legal advice.