2024-02-12T03:41:16Z

A private (also called secret) key is a handful of bytes of randomly-generated data chosen for certain desirable mathematical characteristics. It is one half of the cryptographic inputs to a public-key cryptosystem, the other half being, predictably, a public key. Also called asymmetric cryptography, all public-key algorithms work on the principle that a certain class of math problem is cheap to compute in one direction, but prohibitively expensive to run the other way. An example of this is prime numbers: cheap to find and multiply together, expensive to pull apart again into factors. Unlike symmetric encryption, which uses the same key to encrypt data as well as decrypt it, in asymmetric encryption you use the recipient's public key to encrypt what you send them, and your private key to decrypt what other people send you. If your private key didn't stay private, then other people would be able to decrypt messages intended only for you.

Private key

Secret key