I downloaded it and I' m using it.
Nice feature the "notepad".... easier for encrypt/sign.

In T3963#114101, @aheinecke wrote:

OOooh yeee.
Ok. Didn't know how bad gpg4usb really is.
I looked into it. Gpg4usb distributes their own binary GPGME version https://github.com/gpg4usb/gpg4usb/tree/master/linbuild/lib I don't even know which version that is. They are in violation of the GPL as they don't offer the source code of that GPGME version.

So, don't use it please what they do is horrible from a security standpoint. Try using Kleopatra (which I personally maintain). And if it does not work for your use case please let us know what your use case is and we can try to make it better for you. :-)

But indeed for gpg4usb you can't expect help here. They are very likely shipping a horribly outdated version with bugs that have since been fixed.

I 'll try GPA and Kleopatra, I hope will do the same tasks.
thanks anyway.

@aheinecke thanks for the post.
When you said "open a new issue" is create here or in Ubuntu forums a new issue ?
I'll do. when ?
I imagine ni some weeks will be solved but I use the tool everyday for secure text.

gpg 2.2.4-1ubunt amd64 GNU Privacy Guard -- minimalist p

I have the same issue with Xubuntu 18.04 lts, and GNUPG.
./start_linux_64bit
[Error] Source: GPGME String: "Invalid crypto engine"
[Error] Source: GPGME String: "Invalid crypto engine"
[Error] Source: GPGME String: "Invalid crypto engine"