我需要加密和解密外部存储中的PDF文件并使用AES算法进行加密。
现在我需要解密加密的文件，尝试解密并获取字节，然后转换为字符串以在textview中显示，但它在textview中以加密形式显示数据...
代码在这里我试过：
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.KeySpec;
import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.SecretKeySpec;
import android.app.Activity;
import android.os.Bundle;
import android.os.Environment;
import android.widget.TextView;
public class FileActivity extends Activity {
private String encryptedFileName = "sample.pdf.aes";//
private static String algorithm = "AES";
static SecretKey yourKey = null;
TextView text;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_file);
// saveFile("Hi friends");
try {
saveFile( new String(loadFile(Environment.getExternalStorageDirectory()+"/pdf.pdf")));
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
text=(TextView)findViewById(R.id.text);
text.setText(decodeFile());
}
public static SecretKey generateKey(char[] passphraseOrPin, byte[] salt)
throws NoSuchAlgorithmException, InvalidKeySpecException {
// Number of PBKDF2 hardening rounds to use. Larger values increase
// computation time. You should select a value that causes computation
// to take >100ms.
final int iterations = 1000;
// Generate a 256-bit key
final int outputKeyLength = 256;
SecretKeyFactory secretKeyFactory = SecretKeyFactory
.getInstance("PBKDF2WithHmacSHA1");
KeySpec keySpec = new PBEKeySpec(passphraseOrPin, salt, iterations,
outputKeyLength);
yourKey = secretKeyFactory.generateSecret(keySpec);
return yourKey;
}
public static SecretKey generateSalt() throws NoSuchAlgorithmException {
// Generate a 256-bit key
final int outputKeyLength = 256;
SecureRandom secureRandom = new SecureRandom();
// Do *not* seed secureRandom! Automatically seeded from system entropy.
KeyGenerator keyGenerator = KeyGenerator.getInstance("AES");
keyGenerator.init(outputKeyLength, secureRandom);
SecretKey key = keyGenerator.generateKey();
return key;
}
public static byte[] encodeFile(SecretKey yourKey, byte[] fileData)
throws Exception {
byte[] data = yourKey.getEncoded();
SecretKeySpec skeySpec = new SecretKeySpec(data, 0, data.length,
algorithm);
Cipher cipher = Cipher.getInstance(algorithm);
cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
byte[] encrypted = cipher.doFinal(fileData);
return encrypted;
}
public static byte[] decodeFile(SecretKey yourKey, byte[] fileData)
throws Exception {
byte[] data = yourKey.getEncoded();
SecretKeySpec skeySpec = new SecretKeySpec(data, 0, data.length,
algorithm);
Cipher cipher = Cipher.getInstance(algorithm);
cipher.init(Cipher.DECRYPT_MODE, skeySpec);
byte[] decrypted = cipher.doFinal(fileData);
return decrypted;
}
void saveFile(String stringToSave) {
try {
File file = new File(Environment.getExternalStorageDirectory()
+ File.separator, encryptedFileName);
BufferedOutputStream bos = new BufferedOutputStream(
new FileOutputStream(file));
char[] p = { 'p', 'a', 's', 's' };
SecretKey yourKey = generateKey(p, generateSalt().toString()
.getBytes());
byte[] filesBytes = encodeFile(yourKey, stringToSave.getBytes());
bos.write(filesBytes);
bos.flush();
bos.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
}
public static byte[] loadFile(String sourcePath) throws IOException
{
InputStream inputStream = null;
try
{
inputStream = new FileInputStream(sourcePath);
return readFully(inputStream);
}
finally
{
if (inputStream != null)
{
inputStream.close();
}
}
}
public static byte[] readFully(InputStream stream) throws IOException
{
byte[] buffer = new byte[8192];
ByteArrayOutputStream baos = new ByteArrayOutputStream();
int bytesRead;
while ((bytesRead = stream.read(buffer)) != -1)
{
baos.write(buffer, 0, bytesRead);
}
return baos.toByteArray();
}
String decodeFile() {
String str = null;
try {
byte[] decodedData = decodeFile(yourKey,loadFile(Environment.getExternalStorageDirectory()+"/sample.pdf.aes"));
str = new String(decodedData);
System.out.println("DECODED FILE CONTENTS : " + str);
} catch (Exception e) {
e.printStackTrace();
}
return str;
}
}
谢谢，如果有任何建议是很有帮助....有没有其他方法来加密和解密PDF文件
答案 0 :(得分：2)
我使用了这段代码
public class FileActivity extends Activity{
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_file);
encryptPDF();
}
public void encryptPDF()
{
//CipherInputStream input=null;
/*FileInputStream fis=null ;
FileOutputStream fos=null;*/
// get the key
try {
final KeyGenerator generator = KeyGenerator.getInstance("AES");
generator.init(128);
final SecretKey secretKey = generator.generateKey();
// perform encryption
Cipher cipher;
cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
cipher.init(Cipher.ENCRYPT_MODE, secretKey);
FileInputStream fis = new FileInputStream(Environment.getExternalStorageDirectory()+"/sample.pdf");
FileOutputStream fos = new FileOutputStream(Environment.getExternalStorageDirectory()+"/pdf_encrypt.enc");
final CipherOutputStream output = new CipherOutputStream(fos, cipher);
int bytesRead = 0;
final byte[] plainText = new byte[4096];
while ((bytesRead = fis.read(plainText)) >= 0) {
output.write(plainText, 0, bytesRead);
}
output.flush();
output.close();
fos.close();
fis.close();
final byte[] iv = cipher.getIV();
// decrypt the file
cipher.init(Cipher.DECRYPT_MODE, secretKey, new IvParameterSpec(iv));
fis = new FileInputStream(Environment.getExternalStorageDirectory()+"/pdf_encrypt.enc");
fos = new FileOutputStream(Environment.getExternalStorageDirectory()+"/test.pdf");
CipherInputStream input = new CipherInputStream(fis, cipher);
final byte[] decryptedData = new byte[4096];
int decryptedRead;
while ((decryptedRead = input.read(decryptedData)) >= 0) {
fos.write(decryptedData, 0, decryptedRead);
}
fos.flush();
fos.close();
input.close();
fis.close();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}