Evidence Preserver

Lock screenshots of chat / SNS bullying into a tamper-evident hash chain. Hand the resulting ZIP to a trusted adult, school, or counselor and prove that the screenshots are in their original order, with their original contents.

Images are never uploaded. Everything runs inside your browser.

We never send anything. Everything runs inside your browser.

⚠️ This is NOT legally admissible evidence

For court-admissible evidence you need a third-party timestamp (a Time Stamping Authority). This tool helps you explain to a third party what you saved and in what order. Reordering and content tampering are detectable, but the "created at" time itself is self-signed (your PC clock).

Drop screenshot images here (multiple allowed)

or choose files

Files are chained top to bottom. Arrange them to match the real timeline.

Future work (not implemented)

Integration with third-party timestamps (e.g. OpenTimestamps) is under consideration. We will not break the fully offline guarantee.

How it works

Each image is hashed with SHA-256.
A hash chain is built: chain[i] = SHA256(chain[i-1] || file_hash[i]). Reordering a single file breaks every chain entry after it.
The final chain value becomes the rootHash stored in manifest.json along with the ISO8601 creation time.
The images and manifest.json are packed into a ZIP named gilga-evidence-YYYYMMDD-HHmmss.zip.
Drop the ZIP into Verify mode to recompute every SHA-256 and chain step and compare against the manifest. Any tampering is flagged in red.

What it can / cannot prove

✅ Detects content tampering (a single byte change fails the check)
✅ Detects reordering of the screenshots
✅ Detects added or removed files
⚠️ The timestamp is your own PC clock (self-signed). It cannot disprove "you faked the time"
⚠️ For court-admissible evidence you need a third-party timestamp authority (TSA) or OpenTimestamps

The primary use case is to explain a situation to a trusted adult, teacher, or counselor with "these happened in this order; I did not edit them." For formal legal action, please consult a lawyer, a notary, or the police.