Termius keeps asking me to provide the passphrase for my PuTTY key

This article explains why during a connection you're asked to provide the passphrase for a PuTTY key after you've already entered the correct passphrase.

The problem occurs with PuTTY keys in the version 3 format, which was introduced and added as the default format for saving keys in PuTTY 0.75. As of now, Termius cannot decrypt this kind of private key.

To make sure you've faced this particular problem, check that the key contains the following line:

PuTTY-User-Key-File-3: ssh-rsa

Solution

Update. Termius has got native support for PuTTY keys in the version 3 format in:

• desktop Termius app 7.23.2 and newer versions,
• iOS Termius app 4.9.7 and newer versions,
• Android Termius app 5.4.5 and newer versions.

For older versions, there are two workarounds for the problem:

1. Converting the key to OpenSSH format via the Conversions > Export OpenSSH key option in PuTTYgen.
2. Resaving the key in the version 2 instead of 3. For that, in PuTTYgen, choose '2' in Key > Parameters for saving key files > PPK file version.