7.7. Verify the chain yourself

To verify the message yourself, you will need 3 set of files. First, you need the secure chain chunk containing the message, then you need the corresponding timestamp and finally the manual signature of the chunk. Contact [e-mail] to receive theses files.

The following java code, using bouncycastle and CSVReader, can be used to validate the chain.

package com.babelway.tools;

import java.io.IOException;
import java.io.StringReader;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.security.Security;
import java.util.Base64;
import java.util.Collection;
import org.bouncycastle.cert.X509CertificateHolder;
import org.bouncycastle.cms.CMSProcessableByteArray;
import org.bouncycastle.cms.CMSSignedData;
import org.bouncycastle.cms.CMSSignerDigestMismatchException;
import org.bouncycastle.cms.CMSVerifierCertificateNotValidException;
import org.bouncycastle.cms.SignerInformation;
import org.bouncycastle.cms.jcajce.JcaSimpleSignerInfoVerifierBuilder;
import org.bouncycastle.jcajce.provider.digest.SHA3;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.util.encoders.Hex;
import au.com.bytecode.opencsv.CSVReader;

public class SecureChainValidator {

    public static void main(String[] args) throws Exception {
        Security.addProvider(new BouncyCastleProvider());
        // # 1. Validate that the part of the secure chain (i.e. the chunk) that you want to verify is self-consistant
        //      The CSV file that contains a part of the secure chain that you want to verify.
        byte[] chunk = Files.readAllBytes(Paths.get("/tmp/chunk.csv"));
        assertChunkFileIsSelfConsistent(chunk);
        System.out.println("The chunk is self consistant!");

        // # 2. Validate the related timestamp
        // The timestamp
        byte[] timestamp = Files.readAllBytes(Paths.get("/tmp/timestamp.txt"));
        assertTimestampIsValid(timestamp);
        System.out.println("The timstamp is valid!");

        // 2. Validate the related manual signature
        // The text file (in JSON format) that contains all the information about all the chunks that
        // were manually signed together, including the target chunk
        byte[] signatureContent = Files.readAllBytes(Paths.get("/tmp/signatureContent.txt"));
        // The signature itself
        byte[] signature = Files.readAllBytes(Paths.get("/tmp/signature.txt"));
        assertSignatureIsValid(signature, signatureContent);
        System.out.println("The signature is valid!");

        System.out.println("Verification finished successfully");
    }


    public static void assertChunkFileIsSelfConsistent(byte[] chunk) {
        try (CSVReader reader = new CSVReader(new StringReader(new String(chunk)), ';', '"', '\\')) {
            String[] row = reader.readNext();
            if (row == null) {
                throw new IllegalArgumentException("Empty chunk file");
            }
            //chaining = chainId;creationMoment;hubId;messageKey;step;hash;previousChainHash
            String chainHash = row[6];
            StringBuilder sb;
            while ((row = reader.readNext()) != null) {
                sb = new StringBuilder();
                for (int j = 0; j