Java Security - RSA 公钥和私钥代码问题

Question

这是我的错误

java.security.spec.InvalidKeySpecException: java.security.InvalidKeyException: IOException: DerInputStream.getLength(): lengthTag=127, too big.
    at sun.security.rsa.RSAKeyFactory.engineGeneratePublic(Unknown Source)
    at java.security.KeyFactory.generatePublic(Unknown Source)
    at com.sanjaya.rsa.PublicKeyReader.get(PublicKeyReader.java:22)
    at com.sanjaya.rsa.MainKeyClass.main(MainKeyClass.java:8)
Caused by: java.security.InvalidKeyException: IOException: DerInputStream.getLength(): lengthTag=127, too big.
    at sun.security.x509.X509Key.decode(Unknown Source)
    at sun.security.x509.X509Key.decode(Unknown Source)
    at sun.security.rsa.RSAPublicKeyImpl.<init>(Unknown Source)
    at sun.security.rsa.RSAKeyFactory.generatePublic(Unknown Source)
    ... 4 more

这是我的代码 - MAIN CLASS

public static void main(String[] args) {
    PublicKeyReader publicKeyReader=new PublicKeyReader();
    try {
        publicKeyReader.get("c:\\public.key");
    } catch (Exception e) {
        e.printStackTrace();
    }

    PrivateKeyReader privateKeyReader=new PrivateKeyReader();
    try {
        privateKeyReader.get("c:\\private.key");
    } catch (Exception e) {
        e.printStackTrace();
    }

这里是公钥相关的方法

  public static PublicKey get(String filename) throws Exception {
    File f = new File(filename);
    FileInputStream fis = new FileInputStream(f);
    DataInputStream dis = new DataInputStream(fis);
    byte[] keyBytes = new byte[(int)f.length()];
    dis.readFully(keyBytes);
    dis.close();
    X509EncodedKeySpec spec =new X509EncodedKeySpec(keyBytes);
    KeyFactory kf = KeyFactory.getInstance("RSA");
    return kf.generatePublic(spec);
  }

这里是私钥相关的方法

  public static PrivateKey get(String filename)throws Exception {
    File f = new File(filename);
    FileInputStream fis = new FileInputStream(f);
    DataInputStream dis = new DataInputStream(fis);
    byte[] keyBytes = new byte[(int)f.length()];
    dis.readFully(keyBytes);
    dis.close();
    PKCS8EncodedKeySpec spec =new PKCS8EncodedKeySpec(keyBytes);
    KeyFactory kf = KeyFactory.getInstance("RSA");
    return kf.generatePrivate(spec);
  }

请帮我解决这个问题

需要创建公钥和私钥并加密，从RSA加密的字符串中解密

Answer 1

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.math.BigInteger;
import java.security.Key;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.spec.KeySpec;
import java.security.spec.RSAPrivateKeySpec;
import java.security.spec.RSAPublicKeySpec;
import javax.crypto.Cipher;
import javax.crypto.CipherInputStream;
import javax.crypto.CipherOutputStream;

class RSA{

public static void main(String[] args) throws Exception {
    generateKeys();
    rsaEncrypt("plaintext.txt", "encrypted.txt");
    rsaDecrypt("encrypted.txt", "decrypted.txt");
}

public static void generateKeys() throws Exception {
    KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
    kpg.initialize(2048);
    KeyPair kp = kpg.genKeyPair();
    PublicKey publicKey = kp.getPublic();
    PrivateKey privateKey = kp.getPrivate();

    System.out.println("keys created");

    KeyFactory fact = KeyFactory.getInstance("RSA");
    RSAPublicKeySpec pub = fact.getKeySpec(publicKey,
            RSAPublicKeySpec.class);
    RSAPrivateKeySpec priv = fact.getKeySpec(privateKey,
            RSAPrivateKeySpec.class);

    saveToFile("public.key", pub.getModulus(), pub.getPublicExponent());
    saveToFile("private.key", priv.getModulus(), priv.getPrivateExponent());

    System.out.println("keys saved");
}

public static void saveToFile(String fileName, BigInteger mod,
        BigInteger exp) throws IOException {
    ObjectOutputStream fileOut = new ObjectOutputStream(
            new BufferedOutputStream(new FileOutputStream(fileName)));
    try {
        fileOut.writeObject(mod);
        fileOut.writeObject(exp);
    } catch (Exception e) {
        throw new IOException("Unexpected error");
    } finally {
        fileOut.close();
        System.out.println("Closed writing file.");
    }
}

// Return the saved key
static Key readKeyFromFile(String keyFileName) throws IOException {
    InputStream in = new FileInputStream(keyFileName);
    ObjectInputStream oin = new ObjectInputStream(new BufferedInputStream(
            in));
    try {
        BigInteger m = (BigInteger) oin.readObject();
        BigInteger e = (BigInteger) oin.readObject();
        KeyFactory fact = KeyFactory.getInstance("RSA");
        if (keyFileName.startsWith("public"))
            return fact.generatePublic(new RSAPublicKeySpec(m, e));
        else
            return fact.generatePrivate(new RSAPrivateKeySpec(m, e));
    } catch (Exception e) {
        throw new RuntimeException("Spurious serialisation error", e);
    } finally {
        oin.close();
        System.out.println("Closed reading file.");
    }
}

// Use this PublicKey object to initialize a Cipher and encrypt some data
public static void rsaEncrypt(String file_loc, String file_des)
        throws Exception {
    FileReader file = new FileReader("C://myprograms//plaintext.txt");
    BufferedReader reader = new BufferedReader(file);
    String text = "";
    String line = reader.readLine();
    while(line!= null)
    {
        text += line;
    line = reader.readLine();
    }
    reader.close();
    System.out.println(text);
    byte[] data = new byte[32];
    int i;

    System.out.println("start encyption");
    Key pubKey = readKeyFromFile("public.key");
    Cipher cipher = Cipher.getInstance("RSA");
    cipher.init(Cipher.ENCRYPT_MODE, pubKey);

    FileInputStream fileIn = new FileInputStream(file_loc);
    FileOutputStream fileOut = new FileOutputStream(file_des);
    CipherOutputStream cipherOut = new CipherOutputStream(fileOut, cipher);

    // Read in the data from the file and encrypt it
    while ((i = fileIn.read(data)) != -1) {
        cipherOut.write(data, 0, i);
    }

    // Close the encrypted file
    cipherOut.close();
    fileIn.close();

    System.out.println("encrypted file created");
}

// Use this PublicKey object to initialize a Cipher and decrypt some data
public static void rsaDecrypt(String file_loc, String file_des)
        throws Exception {
    byte[] data = new byte[32];
    int i;

    System.out.println("start decyption");

    Key priKey = readKeyFromFile("private.key");
    Cipher cipher = Cipher.getInstance("RSA");
    cipher.init(Cipher.DECRYPT_MODE, priKey);

    FileInputStream fileIn = new FileInputStream(file_loc);
    CipherInputStream cipherIn = new CipherInputStream(fileIn, cipher);
    FileOutputStream fileOut = new FileOutputStream(file_des);

    // Write data to new file
    while ((i = cipherIn.read()) != -1) {
        fileOut.write(i);
    }

    // Close the file
    fileIn.close();
    cipherIn.close();
    fileOut.close();

    System.out.println("decrypted file created");

}
}

本程序对plaintext.txt文件中的文本进行加密，并将密文保存在encrypted.txt文件中。类似地，解密是使用 encrypted.txt 文件完成的，纯文本保存在 decrypted.txt 文件中。#