Most privacy problems are not sophisticated attacks. They are a friend scrolling through your phone, a family member picking it up, or someone glancing over your shoulder at your home screen.
For these situations, the cover helps:
We also kept the look deliberately grown-up and plain: flat surfaces, system type, one muted accent colour. Bright, cartoonish design draws attention, which is the opposite of what we want.
A disguise is only a disguise. It is worth being clear about its limits:
The protection comes from encryption and from your password:
This means the most important decision is your password. A few random words, such as “copper lantern orbit meadow”, is far stronger than a short word with a number, and still easy to remember. The app shows a strength estimate when you choose it.
The cover decides whether anyone notices the vault. The encryption decides whether anyone can open it. You should rely on the second and treat the first as a convenience.
For the full design and its limitations, see the security design.
]]>Moving it takes a couple of minutes.
.hhbits file somewhere you can reach from the new phone: AirDrop it to your Mac, save it to Files, or copy it to a USB drive.Keep the app open until the export finishes. If the app locks during an export, the export is cancelled, so the key is never kept in the background.
Your folders, files and password come back exactly as they were. From then on, type your password where the app asks for your name.
The backup is the vault’s own ciphertext, packed into a single file. It is never decrypted or re-encrypted along the way, so it is as strong as the vault itself.
A regular backup is the simplest way to own your data without depending on anyone else’s infrastructure.
]]>When you type your password, the app first normalizes it (Unicode NFC), so the same text always produces the same key regardless of how the keyboard encoded it. Any characters are allowed, including spaces and emoji.
The password is then run through Argon2id, a password hashing function designed to resist guessing on specialised hardware. We use 3 passes over 256 MiB of memory with a random salt. On an iPhone this takes about a second. For someone trying millions of guesses, it makes each one expensive.
The password-derived key does not encrypt your files directly. Instead, it unwraps a random 256-bit master key that was generated when you created the vault. The master key is stored wrapped with AES-256-GCM.
This has a practical benefit: changing your password only re-wraps the master key. A vault with gigabytes of video can change its password in a moment.
From the master key, the app derives a separate key for each blob (each file, each thumbnail and the index that holds names and folders) using HKDF-SHA256. Keys are never reused across items.
Because names and folder structure live inside the encrypted index, someone looking at the app’s storage sees only opaque blobs.
Files are split into 1 MiB chunks, each encrypted with AES-256-GCM. GCM authenticates as well as encrypts, so any change to the ciphertext is detected.
Each chunk’s authentication also covers its position and whether it is the final chunk. That closes off three quieter attacks:
Chunking also lets the app play video and audio without decrypting a whole file. The player asks for a byte range, and only the chunks covering that range are decrypted, in memory.
Photos, notes, PDFs and text are decrypted in memory and shown directly. A few features, such as sharing a file to another app or previewing an unusual format with Quick Look, need a real file. In those cases the app writes a temporary copy and deletes it when you close the preview and whenever the vault locks.
The vault locks the moment the app leaves the foreground. If an unlock, import or note save is still running at that point, it is cancelled or discarded. A closed session can never write to disk again. On top of this, the vault’s files use iOS FileProtection.complete, so the system also keeps them encrypted while the phone itself is locked.
None of these primitives are new. That is deliberate. Argon2id, HKDF and AES-GCM are widely reviewed, and we use them through Apple CryptoKit and libsodium rather than our own implementations. The work is in combining them carefully and being clear about what the result does and doesn’t protect.
For the full list, including known limitations, see the security design.
]]>Hedgehog Bits takes a different approach. It is a vault for notes, photos, videos and documents that lives entirely on your iPhone. We don’t run servers for it, we don’t ask for an account, and we never receive your data. There is nothing on our side to breach, subpoena or misuse.
“You own your data” is easy to write in a privacy policy. We wanted it to be a property of the design instead:
We think that last point deserves to be said plainly. A recovery option means someone other than you holds a way in. We chose not to build one.
When you open Hedgehog Bits, you see a line-art hedgehog and a simple question: “Who is playing?” Type your vault password and the vault opens. Type anything else and the app greets you and offers ten short brain games.
The goal is discretion. An app called “Secret Vault” on a home screen invites questions. A calm game with a hedgehog does not. We wrote more about what this cover can and cannot do in a separate post.
We use well-studied building blocks with conservative settings: Argon2id for the password, a random 256-bit master key, per-item keys derived with HKDF, and AES-256-GCM for content. The security design page lists the details, including the limitations.
We’ll use this blog to explain how the app works and to share practical advice on keeping private data private. If you have questions, the FAQ is a good place to start.
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