Encryption is a process of converting information or data into a code to prevent unauthorised access. It involves the use of algorithms (mathematical procedures or formulas) to transform plaintext, which is the original and readable data, into ciphertext, which is the encrypted and unreadable form. The encryption process typically requires a key, which is a specific piece of information used in conjunction with the algorithm to perform the encryption and, later, the decryption.

The primary purpose of encryption is to ensure the confidentiality and security of sensitive information during storage or transmission. Encryption is widely used in various applications, including secure communication over the internet, safeguarding personal information, protecting financial transactions, and securing sensitive data on storage devices. There are different types of encryption algorithms, and the strength of encryption often depends on factors such as the length of the encryption key and the complexity of the algorithm used.

Symmetric encryption involves the use of one key for both encryption and decryption. The plaintext is fed into an encryption algorithm along with a key. The algorithm uses the key to turn the plaintext into ciphertext, thus encrypting the original sensitive data. This works well for data that is being stored and needs to be decrypted at a later date. The use of just one key for both encryption and decryption reveals an issue, as the compromise of the key would lead to a compromise of any data the key has encrypted. This also does not work for data-in-motion, which is where asymmetric encryption comes in.

Asymmetric encryption works with a pair of keys. The beginning of asymmetric encryption involves the creation of a pair of keys, one of which is a public key, and the other is a private key. The public key is accessible by anyone, while the private key must be kept a secret from everyone but the creator of the key. This is because encryption occurs with the public key, while decryption occurs with the private key. The recipient of the sensitive data will provide the sender with their public key, which will be used to encrypt the data. This ensures that only the recipient can decrypt the data, with their private key.

Finally, it is important to explain end-to-end encryption, which offers an additional layer of protection. End-to-end encryption (E2EE) keeps information encrypted and private from everyone, including the provider of the online service. For example, on end-to-end encrypted messaging services, the sender is one “end” of the conversation and the recipient is the other “end”, which leads to the name “end-to-end”. Basically, it's like when you send a scrambled letter through a postal service, nobody can read your letter except you and the person to whom you sent it.