Became invalid signature after granting a valid signature

Hello.

Adobe reader shows invalid signature after granting a valid signature.

I show how to reproduce the problem.

I attached 3 PDF files.

1) Original PDF file : HelloWorld_original.pdf

2) Edit PDF file : HelloWorld_edited.pdf

3) Add timestamp : HelloWorld_edited_timestamped.pdf

And also attached 2 image files.

A) ValidTimestamp.png

B) InvalidTimestamp.png

Using Adobe Reader, open the original file 1).

On the Adobe Reader, select

Tools -> Fill & Sign

and edited the file.

After that, save the file as 2).

On the Adobe reaader, select 

Tools -> Certificates (before this, you need to add a default timestamp server)

and timestamp with "Time Stamp" menu.

The file was saved as 3).

On the Adobe Reader, hit "F4", then you can show the timestamp signature as valid.

See image file: ValidTimestamp.png

After that reopen the file 3).

Then you can show the timestamp signature as invalid.

See image file: InvalidTimestamp.png

The cause of this problem seems Adobe Reader cannot save the correct PDF file 2),3),  when reopend, it corrects the PDF file, therefore, the content to be signed is changed.

The following is my Adobe Reader information:

Adobe Acrobat Reader DC

Continuous Release | Version 2022.001.20142 | 64-bit

Version File Version: 22.001.20142.0

AGM Version 4.030.00117 | 64-bit

CoolType Version 5.017.00011 | 64-bit

Core Version 22.256 | 64-bit

JP2K Verion 2.000.00006.50420 | 64-bit

Here is my OS Verion:

OS: Windows 10 Enterprise

Version: 21H2

Build: 19044.1766

I guess most Adobe Reader can reporoduce the problem.

Regards,

Koichi Sugimoto.