In asymmetric cryptography, a private key is a very large random number that only you should know. Anyone who gets hold of it can effectively move all the assets tied to it, and no bank or support team can stop them.
Relationship to the public key#
A public key is derived from the private key, and the wallet address from that. This path is one-way, meaning you cannot work out the private key from the address. You can give the address to anyone to receive funds, but never the private key.
Example#
An address is like a mailbox number: anyone can drop a letter in. The private key is like the key to that mailbox: only whoever holds it can take out the contents.
Digital signature#
When you send a transaction, the wallet signs it with the private key. The network verifies the signature with the public key without the private key being revealed.
Protecting it#
- Never enter it in an email, messenger, photo, or website
- No genuine support team of any service will ask for it
- Keep a secure offline backup
- Losing it means permanently losing access
- Most thefts happen through phishing or malware, not by breaking the cryptography