1. Download the homebrew you want to sign for 4.21, Later, we must use PkgView to extract the contents of the pkg from our PC. Drag the pkg in the program, right mouse button on the folder and press extract to source folder.
2. Open the folder you just extracted, SDISABLER > USRDIR > EBOOT (SDISABLER in this example, for other pkg is different) click right mouse button and copy the reboot. Now we will need the 4.21 eboot resigner for the next step, open the program folder, and paste the eboot you copied earlier.
3. We launch the resigner, we select the operation 2 NPDRM resigner reboot, then press 2.
4. We will be asked to enter the content-id of the application, in order to obtain what we need is the program pkg content id.
5. Open pkg contet id, loaded the pkg, and once that you will see your id, just copy it and paste it into your resigner and hit enter.
6. Now go back on the resigner folder and copy now EBOOT.
7. Paste it in your pkg folder (SDISABLER\USRDIR).
8. Now after you have fixed the eboot, we need repack pkg; and to do this we need the application psn_package_npdrm . Open program folder and copy file in your pkg folder.
9. Before proceeding to Repack we must configure the package.conf file, open notepad and edit the data as shown in photo.
10. Now SHIFT+right click for open windows command and type "psn_package_npdrm.exe package.conf SDISABLER" where SDISABLER is the id of your game.
11. Done. Your homebrew is now signed for 4.21 CFW... Enjoy