Digital Signature
A cryptographic mechanism that proves authorization of a Bitcoin transaction without revealing the private key. Every valid Bitcoin transaction must carry a digital signature produced by the private key controlling the coins being spent.
A digital signature is a cryptographic mechanism that allows someone to prove they authorized a message or transaction without revealing the secret that gives them that authority. In Bitcoin, digital signatures are the primary way a user proves ownership of their coins and authorizes a transfer. Every Bitcoin transaction must include a valid signature to be accepted by the network.
The process works as follows: a private key is used to create a signature over the transaction data. Anyone can verify this signature using the corresponding public key — confirming that only the holder of the private key could have produced it — without ever learning what the private key is. This asymmetry is what makes the system secure: the private key remains secret, but proof of its use is publicly verifiable.
Digital signatures in Bitcoin use a scheme called ECDSA (Elliptic Curve Digital Signature Algorithm), with the secp256k1 curve. When you send Bitcoin, your wallet automatically creates a signature using your private key. Nodes on the network verify the signature against your public key before accepting the transaction. If the signature is invalid, the transaction is rejected. No institution or intermediary is involved in this authorization — the mathematics does the work.