Private Key

A private key is a long string of letters and numbers (256-bit number) that serves as the cryptographic proof of ownership for a blockchain address. It's used to sign (authorize) transactions.

How it works: - Your private key generates your public key (one-way mathematical function) - Your public key generates your wallet address (what you share to receive funds) - You use your private key to sign transactions (proving you own the funds) - Others verify the signature using your public key (without learning your private key)

Private key vs. seed phrase: - Seed phrase: master backup that can generate ALL your private keys - Private key: specific key for one address - Most users interact with seed phrases rather than raw private keys

"Not your keys, not your coins": this popular phrase means that if you don't control the private keys (e.g., your crypto is on an exchange), you don't truly own the crypto. The exchange controls it. FTX's collapse in 2022 proved this when customers lost billions held on the platform.

Best practice: for significant holdings, self-custody with a hardware wallet gives you direct control of your private keys.

According to Chainalysis (2023), the collapse of FTX in November 2022 resulted in approximately $8.7 billion in customer funds being trapped or lost — the largest single demonstration of why "not your keys, not your coins" remains the foundational security principle in crypto.