Private key
The secret code a crypto wallet owner uses to sign a transfer. Whoever knows the private key controls the assets: the key cannot be recovered, and ownership is confirmed not by an intermediary but by the signature on the blockchain itself.
A private key is a secret sequence that gives the right to dispose of assets on a blockchain. Technically it is a random number of enormous length; the public key and the wallet address are derived from it mathematically, but the reverse path — from the address back to the private key — is computationally infeasible. Owning an asset here means exactly one thing: knowing the key that allows an outgoing transaction to be signed.
How the signature works
The key pair is asymmetric. The network uses the public key to verify a signature and the private key is used to create it. When the owner sends a transfer, the wallet takes the contents of the transaction, reduces them to a hash and produces a signature with the private key. Any node on the network checks the signature against the public key of the sending address: if they match, the transaction is accepted; if not, it is rejected. The private key itself never leaves the wallet in the process and never ends up on the blockchain.
Memorising such a sequence by hand is impossible, so wallets display it as a mnemonic phrase made up of a set of words — from it a deterministic algorithm unfolds the entire hierarchy of keys and addresses. The phrase is equivalent to the key: whoever has seen it has gained access, and it does not matter where the device itself is kept.
What a private key does not have
A private key has no administrator who will confirm the owner's identity and issue a duplicate. There is no registrar of rights here and no intermediary keeping the client's account — the role that a depositary performs on an organised market is taken over on the blockchain by the signature. A lost key means the assets remain on the network forever, but nobody can dispose of them.
Buying through an intermediary is a separate arrangement. A client of an exchange or an exchange operator sees a balance in their personal account, but the private key is held by the platform; the client holds a claim on the platform, not an asset on the network. On the Russian market such transactions are restricted by category of investor: the annual limit on purchases of digital currency by a non-qualified investor from a single intermediary is RUB 300,000, while the instrument is available without a limit to those who have obtained the status of qualified investor. Below are the assets in which turnover is most heavily concentrated:
| # | Security | Value |
|---|---|---|
| 1 | BTCBitcoin | 1,663.66 bn USD |
| 2 | ETHEthereum | 304.56 bn USD |
| 3 | USDTTether | 184.11 bn USD |
As of trading date: 10/10/2026
Where the term is misunderstood
The main misconception is to treat a private key as a password. A password is stored on a server and is reset through customer support; a private key is stored nowhere except in the owner's wallet and cannot be reset. The second mistake is to confuse a private key with an access key to a trading interface: an API key issued by a broker or a trading platform is revocable and limited in its permissions, whereas a private key cannot be revoked — the only option is to move the assets to a new address.