Why Are Keys Certified?

[SP] Key certificates are an important element in the use of public-key cryptography (PKC). Your browser, when it visits a secure site, checks for a key certificate from a small number of commercial certificate providers. The instructions that came with PGP described how to sign keys, and explained the importance of doing so. The concept of a public-key infrastructure (PKI) refers to what is essentially a way to facilitate key certification, perhaps with government assistance.