What is a Private Key?
A private key is a secret cryptographic key used to sign transactions and prove ownership of digital assets.
What Does Private Key Mean?
A private key is a piece of secret information used to generate digital signatures that prove the authorization to spend crypto assets. If someone obtains this key, they can sign valid transactions for the associated assets just like you. Therefore, a private key is never shared in the same way a wallet address is.
Assets are not physically stored inside the key file. Blockchain records maintain the conditions under which funds can be spent; the private key produces the signature that meets these conditions. The fact that assets are not deleted from the network if a device breaks explains why having a backup is so crucial.
Difference from a Password
A wallet application password might protect the opening of the key file on that specific device. However, if the private key itself is compromised, changing the app password is not enough. An attacker can use the key in different software. An exchange account password is also different; on an exchange, private keys are mostly managed by the service provider.
Modern wallets generally derive a large number of keys from recovery words. These words, known as a seed phrase, may not look the same as a single private key, but they can reconstruct an entire wallet. Both must be kept secret.
How to Protect It
Do not send a private key to a support chat, web form, or through screen sharing. Such information is not required to examine a wallet address or transaction ID. Hardware wallets aim to perform the signing process without ever exposing the key to a computer; however, the recipient and amount should still be verified on the device’s screen.
If you suspect your key has fallen into someone else’s hands, simply disconnecting the wallet from a site is not a solution. You need a wallet created with new keys in a secure environment. Typing the recovery words of an old wallet into a new application does not create a new key; it simply reinstalls the same spending authority.