Signal provides:
- Excellent protection against third party interception of communications (wiretapping).
- Limited protection against compromised (hacked) or lost devices
- No protection against certain common usage mistakes (accidentally including a reporter in your large group war planning chat).
If you look at the systems that are supposed to be used for classified communications, the underlying cryptography isn’t particularly different from Signal (the AES cipher can be used to protect classified material). That’s not what failed here.
The difference is that systems like Signal are designed to *facilitate* communication with anyone. Classified systems are designed to *limit* communication to authorized recipients.
Both are sensible for their respective - very different - purposes.
Matt Blaze
KuJoe 💞
Raglan Niall 
Tanguy ⧓ Herrmann