如何在Java中存储和重用密钥对？

我想要生成一次密钥对并重用它.

public static KeyPair generateKeyPair() throws Exception {
        KeyPairGenerator generator = KeyPairGenerator.getInstance("RSA");
        generator.initialize(2048,new SecureRandom());
        KeyPair pair = generator.generateKeyPair();

        return pair;
}

我该怎么做？

解决方法

这里有一个问题：Java的重点几乎完全在于TLS和实现TLS所需的加密.对于TLS,需要私钥和证书.所以你会遇到这样的情况：

>必须生成(伪造)自签名证书以使用您的公钥或;
>必须找到另一种存储没有证书的私钥的方法.

但是,使用(2.),您很快就会得到一种不兼容的方法.如果你想这样做,你可以创建一个使用PB​​E / CBC加密的PKCS#8加密私钥.

所以这里有一些代码来创建自签名证书并使用它来存储密钥.注意到期日期,您可以将其设置为100年以保证安全(或者您实际上可以进行一些密钥管理).

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.math.BigInteger;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.KeyStore;
import java.security.KeyStore.Entry;
import java.security.KeyStore.PrivateKeyEntry;
import java.security.KeyStoreException;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.Provider;
import java.security.PublicKey;
import java.security.SecureRandom;
import java.security.Security;
import java.security.UnrecoverableEntryException;
import java.security.cert.Certificate;
import java.security.cert.CertificateException;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.util.Calendar;
import java.util.Date;

import org.bouncycastle.asn1.x500.X500Name;
import org.bouncycastle.asn1.x509.SubjectPublicKeyInfo;
import org.bouncycastle.cert.X509CertificateHolder;
import org.bouncycastle.cert.X509v3CertificateBuilder;
import org.bouncycastle.cert.jcajce.JcaX509CertificateConverter;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.operator.ContentSigner;
import org.bouncycastle.operator.OperatorCreationException;
import org.bouncycastle.operator.jcajce.JcaContentSignerBuilder;

public class StoreKeyPair {
    public static KeyPair generateKeyPair() throws Exception {
        KeyPairGenerator generator = KeyPairGenerator.getInstance("RSA");
        generator.initialize(2048,new SecureRandom());
        KeyPair pair = generator.generateKeyPair();

        return pair;
    }

    public static Certificate selfSign(KeyPair keyPair,String subjectDN)
            throws OperatorCreationException,CertificateException,IOException
    {
        Provider bcProvider = new BouncyCastleProvider();
        Security.addProvider(bcProvider);

        long now = System.currentTimeMillis();
        Date startDate = new Date(now);

        X500Name dnName = new X500Name(subjectDN);

        // Using the current timestamp as the certificate serial number
        BigInteger certSerialNumber = new BigInteger(Long.toString(now));

        Calendar calendar = Calendar.getInstance();
        calendar.setTime(startDate);
        // 1 Yr validity
        calendar.add(Calendar.YEAR,1);

        Date endDate = calendar.getTime();

        // Use appropriate signature algorithm based on your keyPair algorithm.
        String signatureAlgorithm = "SHA256WithRSA";

        SubjectPublicKeyInfo subjectPublicKeyInfo = SubjectPublicKeyInfo.getInstance(keyPair
                .getPublic().getEncoded());

        X509v3CertificateBuilder certificateBuilder = new X509v3CertificateBuilder(dnName,certSerialNumber,startDate,endDate,dnName,subjectPublicKeyInfo);

        ContentSigner contentSigner = new JcaContentSignerBuilder(signatureAlgorithm).setProvider(
                bcProvider).build(keyPair.getPrivate());

        X509CertificateHolder certificateHolder = certificateBuilder.build(contentSigner);

        Certificate selfSignedCert = new JcaX509CertificateConverter()
                .getCertificate(certificateHolder);

        return selfSignedCert;
    }

    public static void main(String[] args) throws Exception {
        KeyPair generatedKeyPair = generateKeyPair();

        String filename = "test_gen_self_signed.pkcs12";
        char[] password = "test".toCharArray();

        storeToPKCS12(filename,password,generatedKeyPair);

        KeyPair retrievedKeyPair = loadFromPKCS12(filename,password);

        // you can validate by generating a signature and verifying it or by
        // comparing the moduli by first casting to RSAPublicKey,e.g.:

        RSAPublicKey pubKey = (RSAPublicKey) generatedKeyPair.getPublic();
        RSAPrivateKey privKey = (RSAPrivateKey) retrievedKeyPair.getPrivate();
        System.out.println(pubKey.getModulus().equals(privKey.getModulus()));
    }

    private static KeyPair loadFromPKCS12(String filename,char[] password)
            throws KeyStoreException,NoSuchAlgorithmException,FileNotFoundException,IOException,UnrecoverableEntryException {
        KeyStore pkcs12KeyStore = KeyStore.getInstance("PKCS12");

        try (FileInputStream fis = new FileInputStream(filename);) {
            pkcs12KeyStore.load(fis,password);
        }

        KeyStore.ProtectionParameter param = new KeyStore.PasswordProtection(password);
        Entry entry = pkcs12KeyStore.getEntry("owlstead",param);
        if (!(entry instanceof PrivateKeyEntry)) {
            throw new KeyStoreException("That's not a private key!");
        }
        PrivateKeyEntry privKeyEntry = (PrivateKeyEntry) entry;
        PublicKey publicKey = privKeyEntry.getCertificate().getPublicKey();
        PrivateKey privateKey = privKeyEntry.getPrivateKey();
        return new KeyPair(publicKey,privateKey);
    }

    private static void storeToPKCS12(
            String filename,char[] password,KeyPair generatedKeyPair) throws KeyStoreException,OperatorCreationException {

        Certificate selfSignedCertificate = selfSign(generatedKeyPair,"CN=owlstead");

        KeyStore pkcs12KeyStore = KeyStore.getInstance("PKCS12");
        pkcs12KeyStore.load(null,null);

        KeyStore.Entry entry = new PrivateKeyEntry(generatedKeyPair.getPrivate(),new Certificate[] { selfSignedCertificate });
        KeyStore.ProtectionParameter param = new KeyStore.PasswordProtection(password);

        pkcs12KeyStore.setEntry("owlstead",entry,param);

        try (FileOutputStream fos = new FileOutputStream(filename)) {
            pkcs12KeyStore.store(fos,password);
        }
    }
}

请注意,我太懒了,无法正确处理异常.

此代码使用稍微修改过的this answer版本,请参阅我的注释,了解我更改代码的原因.

公钥当然也可以单独存储.只需调用getEncoded并存储生成的SubjectPublicKeyInfo结构.