A secure system should provide several assurances such as confidentiality, integrity, and availability of data as well as authenticity and non-repudiation. When used correctly, crypto helps to provide these assurances. Cryptography can ensure the confidentiality and integrity of both data in transit as well as data at rest. It can also authenticate senders and recipients to one another and protect against repudiation.
Software systems often have multiple endpoints, typically multiple clients, and one or more back-end servers. These client/server communications take place over networks that cannot be trusted. Communication occurs over open, public networks such as the Internet, or private networks which may be compromised by external attackers or malicious insiders. Originally, cryptography was simply considered the process of hiding information. Nowadays, cryptography is used for much more than that. Cryptography is used for authentication, integrity, and confidentiality. One of the most common ways of implementing cryptography involves the implementation of a Public Key Infrastructure (PKI)