계약 인감 검증의 Java 기술 모범 사례

File certificateFile = new File("certificate.crt");
File contractFile = new File("contract.pdf");

// 加载证书文件和合同文件
CertificateFactory cf = CertificateFactory.getInstance("X.509");
Certificate certificate = cf.generateCertificate(new FileInputStream(certificateFile));
byte[] contractBytes = Files.readAllBytes(contractFile.toPath());

// 初始化Signature对象
Signature signature = Signature.getInstance(certificate.getSigAlgName());
signature.initVerify(certificate.getPublicKey());

// 更新合同文件
signature.update(contractBytes);

// 验证签名
boolean valid = signature.verify(signatureBytes);
if (valid) {
    System.out.println("合同签名验证成功");
} else {
    System.out.println("合同签名验证失败");
}

// 加载合同文件和电子印章
File contractFile = new File("contract.pdf");
File sealFile = new File("seal.png");

// 对比两个文件的哈希值
String contractHash = getHash(contractFile);
String sealHash = getHash(sealFile);

if (contractHash.equals(sealHash)) {
    System.out.println("合同电子印章验证成功");
} else {
    System.out.println("合同电子印章验证失败");
}

// 计算文件的哈希值
private static String getHash(File file) throws IOException, NoSuchAlgorithmException {
    byte[] fileBytes = Files.readAllBytes(file.toPath());
    MessageDigest md = MessageDigest.getInstance("SHA-256");
    byte[] hashBytes = md.digest(fileBytes);

    StringBuilder sb = new StringBuilder();
    for (byte b : hashBytes) {
        sb.append(String.format("%02x", b));
    }

    return sb.toString();
}