Elementary Information Security, 3rd Edition

▶ 8.3 Public-Key Cryptography

When we encrypt with a secret-key algorithm, the security resides in the key, and our data remains secret if our key remains secret. We often call this secret-key cryptography. With public-key cryptography, clever mathematics allows us to share a crypto key publicly and still keep information safe.

Here is an example with Bob and Alice:

Alice, Bob, Eve, and other friends share files through a collection of USB drives that hang on hooks on a corkboard. Different people use different crypto techniques.

Alice read up on public-key techniques, acquired some software, and has convinced Bob to use it. Alice’s software constructed two encryption keys for her. One is a private key that she keeps secret from everyone, ...