Understanding Public-Key Infrastructure: Concepts, Standards, and Deployment Considerations

Public/Private Key Pair

As discussed in the previous section, asymmetric ciphers make use of two related but different keys. In this key pair, the keys are sufficiently different that knowing one does not allow derivation or computation of the other (even for a determined adversary with a lot of computing power at his/her disposal). This means that one of the keys may be made publicly available (for example, stored in an open database, listed in a telephone book, or printed on a business card) without reducing security—provided that the other key remains private. The idea that one of the keys in this pair can be revealed publicly was so radical and appealing that this whole method of protecting data quickly became known as public–key cryptography ...