如何从pem文件加载公共证书？

我试图从下面的文件中提取RES公钥

-----BEGIN CERTIFICATE----- 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 -----END CERTIFICATE----- 

这是我做的代码..

 public static PublicKey loadPublicKeyFromFile(File publicKeyFile) throws Exception { FileReader file = new FileReader(publicKeyFile); PemReader reader = new PemReader(file); X509EncodedKeySpec caKeySpec = new X509EncodedKeySpec(reader.readPemObject().getContent()); KeyFactory kf = KeyFactory.getInstance("RSA"); PublicKey caKey = kf.generatePublic(caKeySpec); return caKey; } 

但它抛弃了

 java.security.InvalidKeyException: IOException: ObjectIdentifier() -- data isn't an object ID 

从文件中提取RES公钥的适当方法是什么？

Answer 1

X.509证书和X509EncodedKeySpec是完全不同的结构，并且尝试将证书解析为密钥将不起作用。 Java的X509EncodedKeySpec实际上是X.509的SubjectPublicKeyInfo，它只是证书的一小部分。

您需要做的是读取并解析证书，然后从证书中提取pubkey。 我不知道这样做的BC方法，但是标准的SunJCE CertificateFactory可以这样做（并且可以读取PEM或DER来启动）这样（调整错误清理和error handling以尝试）：

  CertificateFactory fact = CertificateFactory.getInstance("X.509"); FileInputStream is = new FileInputStream (args[0]); X509Certificate cer = (X509Certificate) fact.generateCertificate(is); PublicKey key = cer.getPublicKey();