The Double Ratchet algorithm is a cryptographic protocol used in secure messaging apps to provide end-to-end encryption. It works by updating encryption keys for every message sent or received, ensuring that even if a key is compromised, previous and future messages remain secure. This process combines two types of key ratchets - one for each party’s messages and one for each session - making it highly resilient against attacks. Double Ratchet is a core component of the Signal Protocol, which is widely used in popular messaging platforms to protect users’ privacy and conversations.