java - 验证 RSA SHA256 签名无法从证书获取私钥

Question

我正在尝试验证从网络服务接收的数据字符串及其 RSA-SHA256 签名，但我完全陷入了从证书加载私钥/公钥的困境。

我有以下代码来从 cer 文件检索信息，我认为它采用 DER 格式，因为它不是典型的 base64 编码:

InputStream in = new FileInputStream(path1);
CertificateFactory factory = CertificateFactory.getInstance("X.509");
X509Certificate cert = (X509Certificate) factory.generateCertificate(in);
System.out.println(cert.toString());

它输出证书的完整信息:

Version: V3
Subject: EMAILADDRESS=...
...
Algorithm: [SHA256withRSA]
...

但是如果尝试使用以下代码加载和检索私钥:

KeyFactory kf = KeyFactory.getInstance("RSA");        
X509EncodedKeySpec bobPubKeySpec = new X509EncodedKeySpec(encodedKey);
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
PublicKey bobPubKey = keyFactory.generatePublic(bobPubKeySpec);
Signature sig = Signature.getInstance("SHA256withRSA");
sig.initVerify(bobPubKey);
sig.update(data_received);
sig.verify(signature_received);

我收到以下异常

 java.security.spec.InvalidKeySpecException: java.security.InvalidKeyException: invalid key format

在 keyFactory.generatePublic 方法中。如果将其更改为generatePrivate，结果相同。

Answer 1

谢谢詹姆斯，按照你的建议，我做了以下工作:

        InputStream in = new FileInputStream(System.getProperty("user.dir") + "\\" + certificateName);
        CertificateFactory factory = CertificateFactory.getInstance("X.509");
        X509Certificate cert = (X509Certificate) factory.generateCertificate(in);
        PublicKey pubKey = cert.getPublicKey();


        Signature sig = Signature.getInstance("SHA256withRSA");
        sig.initVerify(pubKey);
        sig.update(xmlContent);

        return sig.verify(headerSignature);