利用Java技术判断合同中公章的真实性与合法性

import java.io.FileInputStream;
import java.io.IOException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class ContractValidation {

    public static void main(String[] args) {
        String contractPath = "path/to/contract.pdf";
        String sealPath = "path/to/seal.png";
        
        try {
            byte[] contractHash = calculateHash(contractPath);
            byte[] sealHash = calculateHash(sealPath);
         
            boolean valid = verifyContract(contractHash, sealHash);
            
            if (valid) {
                System.out.println("公章验证通过，合同有效！");
            } else {
                System.out.println("公章验证失败，合同可能被篡改！");
            }
        } catch (IOException e) {
            e.printStackTrace();
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        }
    }
    
    public static byte[] calculateHash(String filePath) throws IOException, NoSuchAlgorithmException {
        FileInputStream fis = new FileInputStream(filePath);
        MessageDigest md = MessageDigest.getInstance("SHA-256");
        
        byte[] buffer = new byte[1024];
        int bytesRead;
        
        while ((bytesRead = fis.read(buffer)) != -1) {
            md.update(buffer, 0, bytesRead);
        }
        
        return md.digest();
    }
    
    public static boolean verifyContract(byte[] contractHash, byte[] sealHash) {
        // 比较合同哈希和公章哈希是否相等
        for (int i = 0; i < contractHash.length; i++) {
            if (contractHash[i] != sealHash[i]) {
                return false;
            }
        }
        
        return true;
    }
}