AES-256 encryption explained in plain words
Almost every app says AES-256. The question that matters is where the key lives.
In short
AES is the encryption standard published by NIST, and AES-256 is the version with 256-bit keys — far too many possibilities to try them all. GCM is a way of using AES that also detects tampering. Because the algorithm is so strong, an app’s real security depends on key management: who holds the key, where it is stored and what unlocks it.
Key takeaways
- AES-256: a NIST standard, 128-bit blocks, 256-bit keys.
- GCM adds an integrity check: altered data fails to decrypt.
- A strong cipher with a badly kept key protects nothing.
What AES is
AES, the Advanced Encryption Standard, is a block cipher selected by the US National Institute of Standards and Technology (NIST) in 2000 and specified in FIPS 197. It transforms data in blocks of 128 bits using a secret key. The standard defines three versions — AES-128, AES-192 and AES-256 — and the number is the length of the key in bits.
It is everywhere, including in your iPhone: setting a passcode turns on data protection, which encrypts your iPhone’s data with 256-bit AES.
Why 256 bits is plenty
A 256-bit key can take 2²⁵⁶ different values. Trying them all is not a question of faster computers: it is far beyond anything that can actually be done. That is why real attacks on well-built systems go around the cipher rather than through it — after the key, the password that unlocks it, or the data while it is decrypted.
What GCM adds
A cipher alone hides data but can’t tell you whether someone changed it. GCM, Galois/Counter Mode, specified by NIST in SP 800-38D, is authenticated encryption: alongside the encrypted data it produces a tag, and if the data or the tag has been altered, decryption fails instead of returning corrupted or manipulated content.
GCM has one strict rule: the value used to start each encryption, called a nonce or IV, must never repeat with the same key. Careful implementations generate a fresh one every time.
Key management is the real question
“AES-256” tells you the lock is strong. It says nothing about where the key is kept. These questions say much more about an app:
- Who holds the key? If the company can reset your access by email, it — or anyone who breaches it — can reach your data.
- Where is it stored? A key saved next to the data, or derived from a short PIN, becomes the weak point.
- What unlocks it? A key protected by your device’s security hardware and a secret only you know is far harder to attack.
- What if you forget the secret? An honest answer involves a recovery key you keep, not a support ticket.
Each file
its own AES-256-GCM key
Vault key
wraps every file key
Secure Enclave
opened by your pattern
How Latent applies it
Latent encrypts each file with its own AES-256-GCM key. Those keys are wrapped by a vault key, itself protected by a key in your iPhone’s Secure Enclave and unlocked by your pattern or password. Keys are erased from memory when the vault locks. Nobody else holds a copy: the nine-word recovery phrase is the only spare, and only you have it.