如何从Base64生成的公钥加密文件
问题描述：
我得到了使用公钥加密给定文件的任务，我必须从给定的Base64指数和模数生成公钥。我使用代码生成了公钥如何从Base64生成的公钥加密文件
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.math.BigInteger;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.RSAPrivateKeySpec;
import java.security.spec.RSAPublicKeySpec;
import javax.crypto.Cipher;
import java.util.Base64;
/**
*
* @author Kunjesh RSA - Encrypt Data using Public Key RSA - Descypt Data using
* Private Key
*/
public class RSAEncryption {
private static final String PUBLIC_KEY_FILE = "Public.key";
public static void main(String[] args) throws IOException {
try {
System.out.println("\n--------SAVING PUBLIC KEY AND PRIVATE KEY TO FILES-------\n");
// Hardcode the RSA key
String modulusString = "qSwYXXE+SQ/ROpCQazST9imW+mPSjiCSjF4s+TFsPpdVln+tL9LrFEVo2ok+97WNg8ZkTEO5atw7uN8FJFXnWAXpQuHBos9/m3Y31nwSaj+CbFr+qdCHFxAq+l7cJUZI7JCCG8GS2365rMBzMSHK0tHcqCNk/EzW+jsBvKumQ7E=";
//String modulusString = "00d56047acf652298e3fcdbb8cecbc32214722aa1625f88480cf570cee373ada932b140c29b00dc44f6e59e7018dddca66b2f1c645dacb9d4a45459cfa8f7e33df";
//String exponentString = "18bc01730656bde47476f7cfbd3d8f9e15ede9c389814672dc161e349b08627fc885fe9d2442ae92f0214c7e97cf0b9a9fc876df4f53517ab63d710f997b2779";
String publicExponentString = "AQAB";
// Load the key into BigIntegers
BigInteger modulus = new BigInteger(Base64.getDecoder().decode(modulusString));
//BigInteger exponent = new BigInteger(exponentString, 16);
BigInteger pubExponent = new BigInteger(Base64.getDecoder().decode(publicExponentString));
// Create private and public key specs
//RSAPrivateKeySpec privateSpec = new RSAPrivateKeySpec(modulus, exponent);
RSAPublicKeySpec publicSpec = new RSAPublicKeySpec(modulus, pubExponent);
// Create a key factory
KeyFactory factory = KeyFactory.getInstance("RSA");
System.out.println("Hello world");
// Create the RSA private and public keys
// PrivateKey priv = factory.generatePrivate(privateSpec);
PublicKey pub = factory.generatePublic(publicSpec);
RSAEncryption rsaObj = new RSAEncryption();
rsaObj.saveKey(PUBLIC_KEY_FILE, modulus, pubExponent);
} catch (Exception e) {
}
}
private void saveKey(String fileName, BigInteger mod, BigInteger exp) throws IOException {
System.out.println("Hello World");
FileOutputStream fos = null;
ObjectOutputStream oos = null;
try {
System.out.println("Generating " + fileName + "...");
fos = new FileOutputStream(fileName);
oos = new ObjectOutputStream(new BufferedOutputStream(fos));
oos.writeObject(mod);
oos.writeObject(exp);
System.out.println(fileName + " generated successfully");
} catch (Exception e) {
e.printStackTrace();
} finally {
if (oos != null) {
oos.close();
if (fos != null) {
fos.close();
}
}
}
}
}
公钥已成功生成。但是，当我这段代码
public void encryptFile(String inputFileName, String outputFileName, String keyFileName) throws Exception {
try {
KeyGenerator keygen = KeyGenerator.getInstance("AES");
SecureRandom random = new SecureRandom();
keygen.init(random);
SecretKey key = keygen.generateKey();
//Packages with the RSA public key
System.out.println("keyFileName : " + keyFileName);
ObjectInputStream keyIn = new ObjectInputStream(new FileInputStream(keyFileName));
Key publicKey = (Key) keyIn.readObject();
keyIn.close();
Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.WRAP_MODE, publicKey);
byte[] wrappedKey = cipher.wrap(key);
DataOutputStream out = new DataOutputStream(new FileOutputStream(outputFileName));
out.writeInt(wrappedKey.length);
out.write(wrappedKey);
InputStream in = new FileInputStream(inputFileName);
cipher = cipher.getInstance("AES");
cipher.init(Cipher.ENCRYPT_MODE, key);
crypt(in, out, cipher);
in.close();
out.close();
} catch (Exception e) {
System.out.println("++++ Exception encryptFile ++++");
e.printStackTrace();
throw e;
}
}
private void crypt(InputStream in, OutputStream out, Cipher cipher)
throws IOException, GeneralSecurityException {
System.out.println("in inside crypt ---- " + in);
System.out.println("in inside crypt ---- " + out);
System.out.println("cipher inside crypt ----- " + cipher);
int blockSize = cipher.getBlockSize();
int outputSize = cipher.getOutputSize(blockSize);
byte[] inBytes = new byte[blockSize];
byte[] outBytes = new byte[outputSize];
int inLength = 0;
boolean done = false;
while (!done) {
inLength = in.read(inBytes);
if (inLength == blockSize) {
int outLength = cipher.update(inBytes, 0, blockSize, outBytes);
out.write(outBytes, 0, outLength);
} else {
done = true;
}
}
if (inLength > 0) {
outBytes = cipher.doFinal(inBytes, 0, inLength);
} else {
outBytes = cipher.doFinal();
}
out.write(outBytes);
}
它显示错误使用产生的密钥给定的文件进行加密
java.lang.ClassCastException：java.math.BigInteger中不能转换到java.security.Key中
发生异常java.lang.ClassCastException：java.math.BigInteger不能转换为java.security.Key
我在哪里错了？帮我..
答
你不能直接将BigInteger投到Key。 A Key应该由两个BigInteger构成，即模数和指数。试试这个：
RSAPublicKeySpec spec = new RSAPublicKeySpec(modulus, publicExponent);
KeyFactory factory = KeyFactory.getInstance("RSA");
PublicKey pub = factory.generatePublic(spec);