No, you cannot "resign" a already "signed for memory card" file.
That's why we extract a file from the PS2 ROM (it uses a "DISC" signature) and there is two types of "DISC" signatures: Bound to disc ID and not bound to disc ID.
The purpose of the "not bound DISC signature" file is allow for encryption on ROM or Hard Disk Drive. It's also the encryption type used on the main elf of the utility discs, which cause the disc to be Magic Gate region specific, thus causing , for example the JP utility discs to not work on asian PS2s.
The bound type will need also the DISC ID to decrypt which makes it even harder to sign the DVD drivers. This is why one cannot install DVD Drivers from copied DVD Driver discs even with modchips disabled and performing swaps.
SCPH-10000_GH-001 SCPH-15000_GH-003 SCPH-18000_GH-008 SCPH-30001_GH-005 SCPH-30000_GH-016(V4) SCPH-30001_GH-010(V4)
2xSCPH-10190, 2xSCPH-10350, 2xSCPH-10280
"**** j0 hackers!"
-Sjeep (As seen on TOXIC OS ELF...)