1. If I use Psiphon open Wi-Fi network, whether I have my personal data to intercept intruders?
When you are connected to Psiphon in whole-device mode, all of your device's traffic is tunneled through a Psiphon server. When you are connected in browser-only mode, only the Psiphon Browser is tunneled. All communication between your device and the Psiphon server, including the tunneled traffic, is encrypted. So other devices on the open Wi-Fi network cannot decrypt your tunneled traffic.
You should also note that the whole-device mode is not active until you press the Start button and see the blue "connected" notification. Psiphon does not have a "start on boot" option. Also, we have noticed in some low memory situations that Psiphon might be killed by the Android OS (even though we have programatically done everything we can to prevent this from happening), so it is important to make sure that the blue Psiphon notification is present indicating that Psiphon is connected.
You should also take note of our privacy policy which is described here:
https://s3.amazonaws.com/57wj-4j1q-wa7e/en/about.html#privacy-policy
2. You write that Psiphon does not provide confidentiality. Only bypassing censorship. So it is safe or not to use? I'm afraid.
Psiphon provides network-layer confidentiality between your device and the Psiphon server. It is designed to bypass censorship, and not specifically designed to provide any extra security at the application layer. That means that it is your responsibility to make sure you are using HTTPS, that you are careful about executing javascript and flash, and that you mitigate any other threats that you are concerned about. Psiphon is also not designed to provide anonymity, nor does it prevent anybody watching your traffic from knowing that you are using Psiphon. You must decide based on your personal circumstances and what you intend to do whether it is safe for you to use Psiphon.
3. You write that Psiphon uses a combination of VPN + SSH + HTTP proxy. And what is the difference from one VPN?
Psiphon for Android builds an SSH tunnel between your device and a Psiphon server. It also runs a local HTTP proxy that establishes connections to websites through the tunnel. In whole-device mode, Psiphon operates just like a VPN (all of your traffic is tunneled through the Psiphon server). In browser-only mode, only the Psiphon Browser is tunneled.
4. What settings are best? What is "Simulating HTTP"? It gives? Why is not enabled by default "Use HTTP proxy when connecting to the network"? What makes this work?
The "Simulating HTTP" option makes the SSH tunnel look very roughly like HTTP traffic. This can be useful when DPI firewalls restrict traffic to HTTP only.
The "Use HTTP proxy" option causes the SSH tunnel to be established through the network's HTTP proxy if one is configured. This is needed on networks that only allow traffic to pass through an HTTP proxy. This is not common so it is not enabled by default.
- The Psiphon Team