What "private" should actually mean

• Client-side (end-to-end) encryption. Your entries encrypt on your device before sync.

• Keys never leave your device. The provider can't decrypt your writing—even if their servers are breached.

• No server-side decryption. Not "just for AI," not "briefly during processing."

• Recovery without backdoors. You hold a recovery key; support can't "peek" or reset your diary.

• Everyday safeguards. App lock (Password/PIN/biometric), clear privacy policy, no ads/data resale.

Definition: A truly encrypted journal app encrypts entries on-device, stores only ciphertext, never keeps your keys, and offers a user-held Recovery Key. That's the bar.

The 10-Minute Privacy Audit (checklist)

Set a timer and run these eight checks on any secure diary app:

1. Find this sentence in the docs: "Keys never leave your device." If it's missing or vague, assume they can decrypt.

2. Look for "ciphertext only" storage. If servers ever see plaintext, it's not end-to-end encrypted.

3. Confirm where encryption runs. You want client-side (iOS/Android/Web/Desktop), typically AES-GCM 256 or equivalent.

4. Recovery story. There should be a Recovery Key you save. You use it to regain access; the company doesn't.

5. App lock. A journal app with password or biometrics blocks casual snooping on shared devices.

6. AI boundaries in plain English. If there are AI features, the policy should say what's processed, where, and what's stored (ideally nothing sensitive).

7. Business model sanity check. Paid product > ad-supported. No data resale. No training on personal entries by default.

Pass/Fail rule: If any of #1–#4 fail, move on.

Which model fits you?

• Offline journal app (local-only). Maximum isolation; manual backups; great if you never sync.

• Cloud journal with server-side decryption. Convenient, but requires trust in the provider with plaintext.

• End-to-end encrypted journal (recommended). Sync across devices while keeping the provider blind to your entries.

Red flags vs green flags

Red flags

• "Encrypted at rest and transit" – this doesn't mean they, or an attacker, can't decrypt

• "We can help you recover your data" (without mentioning a user-held Recovery Key)

• Broad "AI training" language on personal entries

• Ads, data resale, or unspecified third-party sharing

Green flags

• Clear line: "keys never leave your device"

• Explicit: "we store ciphertext only"

• Algorithm + location: "AES-GCM 256, encrypted locally"

• Recovery Key flow you control

• Password/PIN/biometric lock

Copy-paste checklist

☐ Keys never leave my device

☐ Server stores ciphertext only (no server-side decryption)

☐ Encryption runs locally (e.g., AES-GCM 256)

☐ Recovery Key I hold (no staff reset)

☐ App lock (Password/PIN/biometric)

☐ Clear AI policy (no raw text stored or used for training by default)

☐ No ads or data resale

FAQ

What is a private journal app?

A writing app that encrypts entries on your device and stores only ciphertext, so the provider can't read them.

Is a password enough?

A password without client-side encryption protects against casual snooping, not against server access or breaches.

How is an end-to-end encrypted journal different?

Your device encrypts entries before sync. The provider never holds decryption keys, so it can't read your writing.

What happens if I forget my password?

Use your Recovery Key. Real E2EE means support can't "reset" or read your diary.

Can I use AI features safely?

Yes—if the app limits processing and doesn't store raw entries. Read the AI section of the privacy docs.

Try BlankSheet against this checklist

BlankSheet is built to pass the audit: client-side encryption, ciphertext-only storage, keys that stay with you, a user-held Recovery Key, app lock, and clear AI boundaries. If privacy has been your blocker, give it a spin and see how it feels to write when your thoughts truly stay yours.

Private Journal App Buyer's Guide (2025): Verify Real Privacy in 10 Minutes