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What is public-key cryptography?
Public-key cryptography uses a pair of linked keys: a private key you keep secret and a public key you can share. What the private key signs, the public key can check, and the private key cannot be worked out from the public one.
What it means for you
Your wallet address comes from your public key, so you can hand it out to receive funds without giving anyone the power to spend. Anyone who sees your private key, or the seed phrase that generates it, gets exactly the power you have; the chain has no second factor.
A common mistake: “My public key and private key are just two passwords for the same wallet.”
In fact: They are not interchangeable. The public key only lets others verify your signatures and pay you; the private key is the one that can spend, and it cannot be derived from the public key.
How it works
NIST describes it as two related keys where, given the public key, deriving the private key is computationally infeasible. A key pair can do two jobs: encryption, where data locked with the public key opens only with the private key, and digital signatures, where the private key signs and anyone verifies with the public key. Bitcoin and Ethereum use the signing side. A Bitcoin private key is 256 bits of random data, deterministically turned into a public key on the secp256k1 curve; an Ethereum address is the last 20 bytes of the Keccak-256 hash of the public key.
Sources: NIST CSRC glossary: public key cryptography, Bitcoin developer guide: transactions, ethereum.org: Ethereum accounts · checked 4 October 2026
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