Most messenger security comparisons stop at "is it end-to-end encrypted?" That question only covers message content. It says nothing about metadata: who you talk to, when, how often, from where.
LINDDUN closes that gap. Created in 2011 by the DistriNet research group at KU Leuven and now cited in the ISO 27550 privacy engineering standard, it breaks privacy into seven distinct threat categories instead of one encryption checkbox:
- Linkability
- Identifiability
- Non-repudiation
- Detectability
- Disclosure of information
- Unawareness
- Non-compliance
We ran Z-TEXT — a zk-SNARKs blockchain messenger built on BitcoinZ — through this framework against six other metadata-focused messengers: Briar, SimpleX, Threema, Wire, Status, and Jami.
Where Z-TEXT ties for #1
Z-TEXT, Briar, and SimpleX tie on four of seven categories:
| Category | Why |
|---|---|
| Linkability | Tor routing built in, opt-in — same model as SimpleX |
| Identifiability | No phone, no email, no SIM — just a 24-word seed |
| Detectability (on-device) | Panic mode + stealth mode, a combination none of the other six apps ship |
| Unawareness | Threat model publicly disclosed |
The honest gap
Z-TEXT doesn't lead on Data Disclosure. The cryptography is built on librustzcash — the same audited codebase behind Zcash — but the Z-TEXT app itself has no independent third-party audit yet. SimpleX is the only messenger in this group of seven that has one, from Trail of Bits in November 2022. Briar, Threema, Wire, Status, and Jami share the same gap.
Built-on-audited-code and audited-as-an-app are different claims. We can make the first one. Not the second, yet.
Architecture notes
- Tor routing is opt-in, not forced — same trade-off SimpleX makes. Turning it on covers wallet and price-check traffic too, since it protects the whole connection rather than a single app's messaging layer.
- On-chain message persistence is also opt-in. Default is local-only. When toggled on, zk-SNARKs shield both content and parties, so what's visible on-chain is a shielded transaction, not who sent what to whom.
Full scoring writeup and sources: https://z-text.org/linddun-score-z-text-vs-7-privacy-messengers/
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