All crypto systems need keys to operate. The strongest crypto system will give zero security protection if a secret or private key falls in the hands of attackers. Hence, the secure handling of cryptographic keys needs equally much attention as the design and implementation of crypto systems. While crypto systems operate automatically in hardware and software, key management also involves policy, user training, organizational processes and interactions, and coordination between all of these elements. This is to ensure that the generation, exchange, storage, use, destruction, and replacement of keys are done in a secure way. With the billions of Internet-connected systems and devices that all require cryptographic communication, the key management challenge is daunting. A public key infrastructure (PKI) is a solution which significantly reduces the complexity of this challenge by providing a secure basis for the exchange of cryptographic keys.