What this checksum tool changes
Rebuild only per-entry MD5 fields in a verified Dark Souls Remastered PC BND4 save.
Verified input boundary
The file must parse as a bounded non-overlapping 11-entry BND4, carry the documented zeroed Remastered discriminator at header bytes 24-31, and successfully decrypt at least one character entry with the documented DSR AES key to a bounded save-format version. Existing MD5 mismatches are allowed as repair targets.
What is deliberately not claimed
No Prepare to Die Edition promotion, Steam account transfer, character/stat/inventory editing, decrypted export, payload recovery, console format, or arbitrary BND4 support is claimed.
Output
A separate .sl2 copy with each entry's first 16 bytes replaced by MD5(IV + encrypted payload); encrypted payload and BND4 structure remain unchanged.
How to use it safely
Close the game, back up the PC .sl2 save, select it locally, inspect the invalid-MD5 count, run repair, and keep the original until the repaired copy loads.
Troubleshooting
A PtDE-style nonzero header discriminator, malformed/overlapping entry table, wrong key fingerprint, or wrong extension fails closed. This tool does not reconstruct damaged encrypted payload.
Verification evidence
Verified with clean and checksum-damaged deterministic AES/BND4 fixtures, independent parser/hash/decryption checks, PtDE/wrong-key/overlap negatives, exact-byte repair, immutable-original checks, and post-write reopen.