How to decrypt an IPA app on macOS?

I see this in logs when I try it:

```
$ ./appdecrypt 1287005205_8.1.ipa D-1287005205_8.1.ipa
Copy From 1287005205_8.1.ipa to D-1287005205_8.1.ipa
Success to copy file.
```

And it just hangs.