Encryption
Also known as: encrypt, encrypted data, cipher, what is encryption
Encryption scrambles data into an unreadable form that can only be turned back with a key, so anyone without the key sees noise instead of your files. It is what protects your phone, backups, and messages if a device is lost or intercepted.
- Scrambles data; only the key can reverse it
- Symmetric uses one key, asymmetric uses a key pair
- Phones encrypt storage by default with a passcode set
How encryption works
Encryption runs your data through a mathematical algorithm (a cipher) together with a secret key. The result, called ciphertext, is unreadable until it is decrypted with the matching key. Without that key, the data is effectively random bytes.
There are two broad styles. Symmetric encryption uses one shared key to lock and unlock — fast, and used for files and disks. Asymmetric (public-key) encryption uses a public key to lock and a private key to unlock, which is how secure messaging and HTTPS exchange keys safely.
Where your devices use it
Modern phones encrypt their entire storage by default, tied to your passcode and a hardware security chip. On iPhone this is on whenever a passcode is set; on Android it is standard on current devices. This is why a strong passcode matters — it guards the key.
Encryption also protects data in transit (HTTPS web traffic), backups (an encrypted iCloud or iTunes backup), and messages. It does not stop you from accidentally deleting files, and it is only as strong as the passphrase protecting the key.