SSH/SFTP Server 0.12.2: Ready for Android 17, Modern SSH Keys and ChaCha20 Encryption

SSH/SFTP Server 0.12.2 is now available on Google Play. This is the biggest update in a long time: the app is ready for Android 17, works with the SSH keys that today's computers create by default, adds the fast ChaCha20-Poly1305 encryption, and gives every installation its own server identity.

Ready for Android 17

Android 17 adds a new privacy permission that every app needs before other devices on your Wi-Fi or wired network can reach it. SSH/SFTP Server is exactly that kind of app: your computer, your file manager and your SSH client all connect to the phone. Without the permission, Android silently blocks them, and the connection just times out.

When you tap Start on Android 17, the app now asks for this permission. Android lists it under Nearby devices. Please allow it, otherwise devices on your network cannot connect. If you skip it, the app explains what will not work and takes you to the settings where you can turn it on later.

Is your phone on Android 16 or older? Then nothing changes for you: there is no new prompt.

Log in with your modern SSH keys

Many users told us that key login did not work and the app kept asking for a password, which is a real problem if you turned password login off. There were several reasons, and all of them are fixed:

• Ed25519 keys now work. It is the key type ssh-keygen creates by default today, and the app could not use it before. You can import Ed25519 public keys in the user editing screen, just like RSA and ECDSA keys.
• RSA keys work with current OpenSSH. Since OpenSSH 8.8, the ssh command refuses the old SHA-1 RSA signatures. The server now supports the modern rsa-sha2-256 and rsa-sha2-512 signatures and tells the client about them, so your RSA key is accepted again.
• 3072-bit RSA keys and ECDSA P-521 keys are accepted. These keys were never matched before, even when they were set up correctly.

If you gave up on key login earlier, it is worth trying again.

Faster encryption: ChaCha20-Poly1305

The server now supports ChaCha20-Poly1305, the encryption that OpenSSH prefers on most systems. It is designed to be fast in software, which helps on phones whose processor has no special hardware for AES. Up-to-date ssh, scp and sftp clients pick it automatically, so you do not need to change anything.

Curious which encryption your connection uses? Run this on your computer and look at the cipher: part:

ssh -v -p 2222 user@phone-ip

A unique server identity for every installation

Every SSH server has a host key: its identity. Your SSH client remembers it the first time you connect and warns you if it ever changes, so nobody can quietly pretend to be your phone.

Until now, the app came with the same host key on every phone. From 0.12.2 on, each new installation creates its own host key on the phone, and it never leaves the device.

If you already use the app, nothing changes automatically. Your current key is kept, so your computers keep connecting without any warning. The app shows you a short notice once, and you can replace the old key whenever it suits you:

1. Open Automation & More settings.
2. Under Host key, you can now see the key's fingerprint, the same value your SSH client shows.
3. Tap Regenerate host key and confirm.

After you regenerate the key, each computer that connected before will show a "REMOTE HOST IDENTIFICATION HAS CHANGED" warning once. That is expected. Remove the old entry with ssh-keygen -R "[phone-ip]:2222" (or accept the new key in your SFTP app) and connect again.

Better battery life

The ad banner in the app now pauses when the app is in the background. Before, it kept waking the phone up several times per second while the server was running, even with the screen off.

Other improvements

• Quick Settings tile: it no longer fails to open the app on Android 14 and newer.
• Back button: works as expected again on Android 16 and newer, including closing the side menu first.
• Up-to-date components: Google Play Billing, ads, crash reporting and other libraries are updated, with their security and stability fixes.

Please note: SSH/SFTP Server now needs Android 6.0 or newer. Phones on Android 5 keep the previous version.

Your users, folders, keys and settings are kept when you update. Get the update from Google Play.