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We will be using a single secret key to encrypt and decrypt our messages, thus having symmetric encryption architecture. Whatsapp uses the Diffie-Helman technique to achieve Asymmetrical encryption, it is one of those techniques which can be used to produce most secure chat applications, if you want to learn more about this, please refer this link. Here is the example of the chat app we are going to build using React and Socket.io with E2E encryption. We will use aes256 package with your secret key.