What end-to-end encrypted actually means.
Nearly every app claims encryption. The word covers three quite different promises, and only one of them means the company can't read your entries.
Three claims that sound alike
- Encrypted in transit. Data is protected while travelling to the server. Standard for any website, and it says nothing about what happens after it arrives.
- Encrypted at rest. The server's disks are encrypted. This protects against stolen hardware, not against the company, an insider or anyone who obtains lawful access, because the service holds the keys.
- End-to-end encrypted. Content is encrypted on your device with a key only you hold. The server stores unreadable ciphertext. Nobody at the company can read your entries, because they can't.
The trade-off nobody mentions
Real end-to-end encryption means the provider cannot reset your access. If you lose the key material, your synced data can't be recovered by anyone. That's the cost of the guarantee, and any app claiming both "we can't read your data" and "we can restore it for you" is describing something weaker.
How RhythmHer's optional sync works
- Sync is off by default; with no account, nothing is uploaded at all.
- Your password is turned into an encryption key on your phone. The password itself never leaves the device, and the value sent for sign-in cannot be used to derive the encryption key.
- Entries are encrypted before upload, so the server stores ciphertext it cannot read.
- At sign-up you get a one-time recovery key. It's the only way back into synced data if you forget your password, so store it somewhere safe.
- Partner sharing sends only the summary you approve, never raw entries, and a log records which categories were shared, never their values.
Questions
Can RhythmHer staff read my synced entries?
No. Entries are encrypted on your device before upload, and the key is derived from a password that never leaves your phone, so the server only holds unreadable data.
What if I forget my password?
Your one-time recovery key restores access to synced data. Without it, encrypted data cannot be recovered by anyone, including us — that is what end-to-end encryption means.
Is sync required to use the app?
No. Core tracking works entirely on your device with no account.
It isn't on the App Store yet. If you'd like to hear when it launches, email [email protected] and we'll let you know. No list, no marketing — just one message.
Read next
RhythmHer provides general educational information and is not a medical device. It does not diagnose or treat any condition and is not a form of contraception. In an emergency, call your local emergency number.