A public key is a shareable cryptographic string used in asymmetric cryptography. In crypto and blockchain systems, it helps identify an account, derive wallet addresses, and enable others to send you funds, all without exposing the private key that controls spending.
How public keys work in asymmetric cryptography
Public key cryptography uses a pair of mathematically related keys: a public key and a private key. The public key can be shared openly, while the private key must remain secret. Depending on the system, the public key may be used to encrypt data that only the private key can decrypt, or to verify a digital signature created by the private key.
In most cryptocurrencies, signatures are the key idea. When you send a transaction, your wallet uses the private key to sign it. Nodes on the network use the corresponding public key to verify that signature, confirming the transaction was authorized by the holder of the private key, without learning the private key itself.
Public keys, wallet addresses, and real-world use
A public key is not always the same as a wallet address. Many blockchains derive an address from a public key using hashing and encoding steps, which can improve usability and add a layer of protection against certain edge cases. In practical terms, you typically share an address to receive funds, but that address ultimately traces back to a public key that can validate spending permissions.
For example, if you provide a donation address, anyone can send crypto to it. Later, when you spend from that address, the network can verify the signature using the relevant public key, ensuring only the rightful key holder can move the funds.
Public keys matter because they enable open participation and verification on public blockchains, supporting secure transactions, self-custody, and trust-minimized systems without relying on a central authority.