Microsoft® Windows® 2000 Security Handbook

Public-Key Cryptography

Public-key cryptography is a system of strong encryption algorithms. It is unique in that there are two keys for each entity: a public key, which is open and can be shared with anyone, and a private key, which is secret and should never be shared. This solution has many benefits, primarily in key management and distribution. Public-key cryptography has uses in encryption, authentication, and digital signatures.

All secure public-key cryptosystems use the idea of "hard problems." They use algorithms considered "one-way trapdoor" problems. This means that the problem is considerably easier to solve one way than the other. Factoring large prime numbers is the hard problem used in many public-key crypto systems. This is also ...