concepts4 min read

Public vs Private Keys

Every wallet is a key pair — a public key (your address) and a private key (your proof of ownership). Understanding this is fundamental to web3 security.

The core concept

Public key → Your address. Share it freely. Anyone can send you tokens or verify your signatures.

Private key → Your secret. Never share it. Whoever has it controls the wallet completely.

Think of it like a mailbox:

The address (public key) is on the mailbox — anyone can send you mail
The key (private key) opens the mailbox — only you can access what's inside

Your public key is mathematically derived from your private key using one-way functions:

Private Key → (one-way math) → Public Key → (hash) → Address

You can always derive the public key from the private key, but you cannot derive the private key from the public key. This is the foundation of blockchain security.

EVM

Private key: 256-bit number (64 hex characters)
Public key: Derived via secp256k1 elliptic curve
Address: Last 20 bytes of the keccak256 hash of the public key, prefixed with 0x

Private: 0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80
Address: 0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266

Solana

Private key: 256-bit number (stored as 64-byte keypair)
Public key: Derived via Ed25519 curve
Address: The public key itself, encoded in Base58

Address: 7nYBm2xGv3WqDzN5Q3JXCH8emhYwpfNKkjFJQ1rQ3kPW

What keys do

Signing

Your private key creates digital signatures — cryptographic proofs that you authorized something. When you:

Send a transaction → you sign it with your private key
Sign a message → you prove you own the address
Approve a contract → you sign the approval transaction

Verification

Anyone with your public key can verify that a signature was created by you, without knowing your private key.

sign(message, privateKey) → signature
verify(message, signature, publicKey) → true/false

Seed phrases (mnemonics)

When you create a wallet, you get a seed phrase — 12 or 24 English words:

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The seed phrase is a human-readable encoding of entropy that generates your private key(s) through a deterministic process:

Seed Phrase → Master Seed → Derivation Path → Private Key → Public Key → Address

Derivation paths

From one seed phrase, you can derive many key pairs using different paths:

m/44'/60'/0'/0/0  → First EVM address
m/44'/60'/0'/0/1  → Second EVM address
m/44'/501'/0'/0'  → First Solana address

This is why one seed phrase can give you addresses on different chains.

Security

What to protect

Private key — full control of the wallet
Seed phrase — can regenerate all private keys
Keystore file — encrypted private key (MetaMask export)

Public key / address — this is public on-chain data anyway
Signatures — these prove you signed something, they don't reveal the private key
Transaction hashes — these are public on-chain records

Attack vectors

Phishing — fake websites that ask you to "enter your seed phrase to verify your wallet"
Malicious signatures — signing a message that's actually a transaction authorization
Clipboard malware — malware that replaces copied addresses with the attacker's address
Social engineering — "support" asking for your seed phrase or private key

Rules

Never share your private key or seed phrase — no legitimate service will ever ask for it
Store seed phrases offline — paper, metal plate. Not in a notes app, screenshot, or cloud storage.
Use hardware wallets for large amounts — the private key never touches your computer
Verify addresses character by character — especially for large transfers
Use separate wallets for risky activities — interact with unknown dApps using a "burner" wallet with minimal funds