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无法匹配使用用于许可应用程序的公钥/私钥生成的密钥大小。我编写了一个自包含的示例，该示例创建公钥/私钥，通过使用公钥签署用户电子邮件地址来创建许可证，然后使用公钥、许可证和电子邮件地址检查许可证确实是使用私钥编码的（显然这不会通常都在一个班级）。

这一切都有效，但是许可证密钥的十六进制版本是 96 个字符（即代表 48 字节/384 位），这比我想要的长一点（相比之下，公钥/私钥的长度不是问题，越长越好）。我可以用什么来生成 32（64 个十六进制字符）字节或 16 个字节（32 个十六进制字符），这样的安全性是否合理？

选择另一种算法有点困难，因为我不了解为生成密钥而选择的算法之间的交互

KeyPairGenerator.getInstance("DSA");

和签名算法

Signature.getInstance("SHA/DSA");

我找不到任何一个列表。

另一点当我生成公钥/私钥对时，我指定密钥大小

keyGen.initialize(1024, new SecureRandom());

然而，公钥（443 字节）或私钥（335 字节）或两者之和（778 字节）都不匹配这个数字。

import org.apache.commons.codec.binary.Hex;

import java.security.*;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

/**
 *
 */
public class CreateLicense
{

    private String PUBLIC_KEY;
    private String PRIVATE_KEY;

    public static void main(final String[] args)
    {
        try
        {
            String email = args[0];
            System.out.println("Creating license for:"+email);
            CreateLicense cl = new CreateLicense();
            cl.generatePublicPrivateKeyPair();
            String license = cl.createLicense(email);
            cl.checkLicense(email, license);

        }
        catch(Throwable t)
        {
            t.printStackTrace();
        }
    }

    //Would only be done once on server
    private void generatePublicPrivateKeyPair() throws Exception
    {
        final KeyPairGenerator keyGen = KeyPairGenerator.getInstance("DSA");
        keyGen.initialize(1024, new SecureRandom());
        final KeyPair pair = keyGen.generateKeyPair();
        PrivateKey privateKey = pair.getPrivate();
        PRIVATE_KEY=Hex.encodeHexString(privateKey.getEncoded());
        PublicKey  publicKey = pair.getPublic();
        PUBLIC_KEY=Hex.encodeHexString(publicKey.getEncoded());
        System.out.println("PrivateKeyHexLength:"+privateKey.getEncoded().length);
        System.out.println("PublicKeyHexLength:"+publicKey.getEncoded().length);

    }

    private PrivateKey reinflatePrivateKey(String keyAsHexString) throws Exception
    {
        byte[] keyBytes = Hex.decodeHex(keyAsHexString.toCharArray());
        final  PKCS8EncodedKeySpec privKeySpec = new PKCS8EncodedKeySpec(keyBytes);
        final  KeyFactory keyFactory = KeyFactory.getInstance("DSA");
        final  PrivateKey privateKey = keyFactory.generatePrivate(privKeySpec);
        return privateKey;
    }

    private PublicKey reinflatePublicKey(String keyAsHexString) throws Exception
    {
        byte[] keyBytes = Hex.decodeHex(keyAsHexString.toCharArray());
        final  X509EncodedKeySpec pubKeySpec = new X509EncodedKeySpec(keyBytes);
        final  KeyFactory keyFactory = KeyFactory.getInstance("DSA");
        final  PublicKey publicKey = keyFactory.generatePublic(pubKeySpec);
        return publicKey;
    }

    //License Create on server based on email address
    private String createLicense(String emailAddress) throws Exception
    {
        String message=emailAddress;
        PrivateKey privateKey =  reinflatePrivateKey(PRIVATE_KEY);
        final Signature dsa = Signature.getInstance("SHA/DSA");
        dsa.initSign(privateKey);
        dsa.update(message.getBytes());
        final byte[] m1 = dsa.sign();
        String license =  Hex.encodeHexString(m1);
        System.out.println("CreateLicense:"+license+":Size:"+license.length());
        return license;
    }

    //Client checks that given known emailaddress and public key that a if a license was derived from
    //that and corresponding privatekey it would match license.
    private boolean checkLicense(String  emailAddress, String license) throws Exception
    {
        String message=emailAddress;
        PublicKey publicKey =  reinflatePublicKey(PUBLIC_KEY);
        final Signature dsa = Signature.getInstance("SHA/DSA");
        dsa.initVerify(publicKey);
        dsa.update(message.getBytes());

        boolean result = dsa.verify(Hex.decodeHex(license.toCharArray()));
        System.out.println("Result"+result);
        return result;
    }
}

给出类似的输出

Creating license for:testuser@nowhere.com
PrivateKeyHexLength:335
PublicKeyHexLength:443
CreateLicense:302c021425f7ad7289b073f82a1d808838f43e0134c5591402140d2a7a4e3967706d4659dc73ace6455040a5fc6b:Size:92
Resulttrue
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1 回答 1

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@Paul - 我认为您的解决方案是使用 ECDSA。更改您的代码行

final KeyPairGenerator keyGen = KeyPairGenerator.getInstance("DSA");

至

final KeyPairGenerator keyGen = KeyPairGenerator.getInstance("ECDSA");

密钥比 DSA 短得多——而且我确信十六进制版本的签名会更短。我建议您使用 256 或 128 位的主要 ECC 曲线。

请让我们知道这是否可以解决问题。

于 2013-02-26T15:07:31.817 回答