Private key
A very large random number that signs transactions. Whoever has it can spend the coins, so it must stay secret.
Private key in more detail
Every wallet is built on three linked pieces: a private key, a public key and an address. One must stay secret and two are safe to share.
A private key is a very large random number. It is 256 bits long, which Ethereum writes as 64 characters. Your wallet creates it for you.
The private key is what signs transactions. Whoever has it can spend the coins. It never needs to leave your wallet, and nobody else ever needs to see it.
All 128 terms · Checked against the lesson's sources on 8 October 2026.
The course by email
Five short emails to get you started, each built on one lesson. After that, one short email a month about what is new. No price tips and no hype.
Free. Unsubscribe any time. See our privacy notice.
Want your progress saved too? Create a free account.