productChain

productChain is a blockchain designed to keep track of valid/verified products. Each transaction in a block is a product Name - Manufacturer ID Pair.

By default, the blockchain has 3 transactions in each block and a set difficulty of 4 These parameters can be changed in the src/blockchain.ts file. Run tsc in the src directory after any changes.

The blockchain uses a Discrete Log ZKP to verify products. This is done as follows,

p is a large prime and g is its generator

A product (with ID x) is sent to an trusted body for verification. After verifying the product, y = g^x mod(p) is calculated and published.

When an external verifier wants to verify if a product is legitimate, they should be able to do so without actually knowing the product's unique ID.

To accomplish this, we use the following Zero Knowledge Proof,

• A random number between 0 and p - 1 is chosen and h = g^x mod (p) is calculated
• h is sent to the verifier. The verifier then send a random bit b (0/1)
• s = (r + bx) mod(p - 1) is calculated and sent to the verifier
• The verifier checks if , g^s mod (p) equals hy^b mod(p)
• This is done for multiple rounds (50 by default in our case). If the equality check fails once, then the productID is not valid

Thus, we are able to verify a productID without actually sending the productID to the verifier

Note : In this repo, a list of randomly generated UUIDs is present in validproductIDs.txt . For testing, only these productIDs will pass the ZKP. This is not a security hazard as the file is not used anywhere in the project.

Running the test network

Run npm install , after cloning the repo.

Run npm run start, to start the peerList.

cd into the src folder to run the nodes.

Each terminal instance can be used to run a node in a randomly selected port,

Run node miner.js in multiple terminals.

Run node api.js in another terminal. The API runs at port 3000 by default.

To view the blockchain: Make a GET request to http://localhost:3000/getChain to get a copy of the blockchain.

To open the frontend, cd into frontend and run npm install , the frontend will open on some open port by default.

Connect each node with its peers [Option 1 in the CLI] before interacting with the blockchain.