This is the physical key that stays in your pocket. Only this specific key can unlock the messages sealed by your public "padlock."
Primarily used for "key exchange," allowing two parties to create a shared secret over an insecure channel. The Quantum Threat Asymmetric Cryptography.epub
In the early days of secret-keeping, if you wanted to send a locked box to a friend, you both needed a copy of the exact same key. This "symmetric" approach worked well until the internet arrived. Suddenly, billions of people needed to exchange secrets with strangers they had never met. How do you share a key without someone stealing it in transit? This is the physical key that stays in your pocket