Describe the precise steps involved in a typical message encryption and decryption process within an end-to-end encrypted system.

The message encryption and decryption process in an end-to-end encrypted (E2EE) system involves a sequence of carefully orchestrated steps designed to ensure that only the intended sender and receiver can access the content of a message. The core principle of E2EE is that the message is encrypted on the sender's device and decrypted on the recipient's device, with no intermediate entities, like the server, having access to the unencrypted message content. The encryption and decryption typically involve a combination of symmetric and asymmetric cryptography, with the key exchange process preceding the actual message transmission. Let's consider a scenario where Alice wants to send a secure message to Bob. The general process is as follows, assuming they have already established a secure shared secret key through a key exchange process using methods such as Diffie-Hellman, which is usually performed prior to transmitting messages: 1. Message Preparation: Alice composes her message, which may be text, images, or other digital content. This is the plain text data that will be encrypted. 2. Key Derivation: A session key (also called a message encryption key) is derived from the shared secret. Typically a new key is used for every message. The key is derived using a cryptographically secure key derivation function or KDF, along with a nonce. The nonce is a random number that's used only once for each message. This adds a crucial layer of security, meaning that even if two messages use the same key, the resulting ciphert....