Cryptography is a technique for secure communication in the presence of third parties called adversaries. An adversary is an entity which is generally malicious in nature, and aims to steal or damage secret data being communicated through a public channel. The theft might be in the form of corrupting data, spoofing the identity of the sender and receiver, disrupting the sending process, injecting their logic into the communicating process, and so on. We can use cryptography in order to achieve a secure communication experience, as shown in the following figure. Here, the sender encrypts the plain text message using the recipient's public key, and then forwards the message to the unsecure channel. On the arrival of the encrypted data, the recipient decrypts the data using its private key.
This is also the basis of cryptography, which is widely used in the modern data transportation system:
