Public key encryption

Traditional encryption systems use the same secret, or key , to encrypt and decrypt a message. So, if a file gets encrypted with the password “bluetonicmonster,” you would need both the file and the password "bluetonicmonster" to decode it. Public key encryption uses two keys: one to encrypt, and another to decrypt. When you sign up to an encrypted messaging service, your phone keeps the key to decrypt messages safely hidden, and sends out the key to encrypt messages to you, so anyone with that key can talk to you securely. The key your phone sends out is known as the "public key": hence the name of the technique. Public key encryption is used to encrypt Signal and WhatsApp messages, and used to enable HTTPS using TLS for web browsing.