2022 Bijeljina Investigation: ZK Photo Redaction

This repository contains the code used to generate and to verify zero knowledge proofs in our 2022 Bijeljina Investigation. The process is used to provably redact regions in authenticated images before they are published.

The following example uses the filename ZKPHOTO, and the following files are involved in the process:

• ZKPHOTO.png: photo to be redacted.
• ZKPHOTO_coords.txt: location of the redaction area on the photo. Each redaction area is a square and listed on a new line in the format of x y width height. For example, a box starting at coordinates x=10px and y=15px with a width of 5px and height of 20px will be represented as 10 15 5 20.
• ZKPHOTO_hash.txt: public hash.
• ZKPHOTO_proof.txt: ZK proof of redaction.
• ZKPHOTO_red.png: redacted photo.
• ZKPHOTO_main.go: gnark Go code to produce the proof.
• verify/ZKPHOTO_main.go: gnark Go code to verify proof.

Creating ZK redaction and generating proof files

Two source files are required in the same folder:

• ZKPHOTO.png
• ZKPHOTO_coords.txt

The code generates the following files:

• ZKPHOTO_hash.txt
• ZKPHOTO_red.png
• ZKPHOTO_proof.txt

The following files are generated but can be purged:

• ZKPHOTO_main.go (used to run Go)
• srs.txt (used to speed up subsequent runs)
• A.txt (used to speed up subsequent runs)

Run:

# Generate proving Go code
python3 redact.py ZKPHOTO

# Run proving Go code to generate proof
go mod tidy
go run ZKPHOTO_main.go ZKPHOTO

Verifying ZK redaction using proof files

Three files are required in the same folder:

• ZKPHOTO_hash.txt
• ZKPHOTO_proof.txt
• ZKPHOTO_red.png

Run:

# Generate verifying Go code 
python3 verify.py ZKPHOTO

# Run verifying Go code to verify proofs
cd verify
go mod tidy
go run ZKPHOTO_main.go ZKPHOTO