我正在编写一个解密文件中存储的文本的Android应用程序。我使用了以下代码 -
public class SimpleCrypto {
public static String encrypt(String seed, String cleartext)
throws Exception {
byte[] rawKey = getRawKey(seed.getBytes());
byte[] result = encrypt(rawKey, cleartext.getBytes());
return toHex(result);
}
public static String decrypt(String seed, String encrypted)
throws Exception {
byte[] rawKey = getRawKey(seed.getBytes());
byte[] enc = toByte(encrypted);
byte[] result = decrypt(rawKey, enc);
return new String(result);
}
private static byte[] getRawKey(byte[] seed) throws Exception {
KeyGenerator kgen = KeyGenerator.getInstance("AES");
SecureRandom sr = SecureRandom.getInstance("SHA1PRNG", "Crypto");
sr.setSeed(seed);
kgen.init(128, sr); // 192 and 256 bits may not be available
SecretKey skey = kgen.generateKey();
byte[] raw = skey.getEncoded();
return raw;
}
private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception {
SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
Cipher cipher = Cipher.getInstance("AES");
cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
byte[] encrypted = cipher.doFinal(clear);
return encrypted;
}
private static byte[] decrypt(byte[] raw, byte[] encrypted)
throws Exception {
SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
Cipher cipher = Cipher.getInstance("AES");
cipher.init(Cipher.DECRYPT_MODE, skeySpec);
byte[] decrypted = cipher.doFinal(encrypted);//this is the line that throws error
return decrypted;
}
public static String toHex(String txt) {
return toHex(txt.getBytes());
}
public static String fromHex(String hex) {
return new String(toByte(hex));
}
public static byte[] toByte(String hexString) {
int len = hexString.length() / 2;
byte[] result = new byte[len];
for (int i = 0; i < len; i++)
result[i] = Integer.valueOf(hexString.substring(2 * i, 2 * i + 2),
16).byteValue();
return result;
}
public static String toHex(byte[] buf) {
if (buf == null)
return "";
StringBuffer result = new StringBuffer(2 * buf.length);
for (int i = 0; i < buf.length; i++) {
appendHex(result, buf[i]);
}
return result.toString();
}
private final static String HEX = "0123456789ABCDEF";
private static void appendHex(StringBuffer sb, byte b) {
sb.append(HEX.charAt((b >> 4) & 0x0f)).append(HEX.charAt(b & 0x0f));
}
}
编辑：这是我试图解密的文本 -
39D4CA73AAF2D42C32659FDC5D1848EA
用这个键 -
thebestsecret153
如果有帮助的话。它应该显示in153。
编辑：在android中抛出错误的行。 -
byte[] decrypted = cipher.doFinal(encrypted);
我还在swing中创建了一个项目来读取文件并得到以下错误 -
javax.crypto.BadPaddingException: Given final block not properly padded
at com.sun.crypto.provider.CipherCore.doFinal(CipherCore.java:811)
at com.sun.crypto.provider.CipherCore.doFinal(CipherCore.java:811)
at com.sun.crypto.provider.CipherCore.doFinal(CipherCore.java:676)
at com.sun.crypto.provider.AESCipher.engineDoFinal(AESCipher.java:313)
at javax.crypto.Cipher.doFinal(Cipher.java:2087)
at decrypt.Decrypt.decrypt(Decrypt.java:43)
at decrypt.MainForm.jButton1MouseClicked(MainForm.java:91)
at decrypt.MainForm.access$000(MainForm.java:20)
at decrypt.MainForm$1.mouseClicked(MainForm.java:46)
at java.awt.AWTEventMulticaster.mouseClicked(AWTEventMulticaster.java:270)
at java.awt.Component.processMouseEvent(Component.java:6508)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3320)
at java.awt.Component.processEvent(Component.java:6270)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4861)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4501)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2719)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:735)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:694)
at java.awt.EventQueue$3.run(EventQueue.java:692)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:708)
at java.awt.EventQueue$4.run(EventQueue.java:706)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:705)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at java.lang.String.<init>(String.java:556)
at decrypt.MainForm.jButton1MouseClicked(MainForm.java:91)
at decrypt.MainForm.access$000(MainForm.java:20)
at decrypt.MainForm$1.mouseClicked(MainForm.java:46)
at java.awt.AWTEventMulticaster.mouseClicked(AWTEventMulticaster.java:270)
at java.awt.Component.processMouseEvent(Component.java:6508)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3320)
at java.awt.Component.processEvent(Component.java:6270)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4861)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4501)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2719)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:735)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:694)
at java.awt.EventQueue$3.run(EventQueue.java:692)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:708)
at java.awt.EventQueue$4.run(EventQueue.java:706)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:705)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)
如果在同一程序中完成加密和解密，它的工作正常。
感谢任何帮助。提前谢谢。
答案 0 :(得分：7)
TL; DR：SecureRandom.getInstance("SHA1PRNG")在播种相同的种子时，可能无法始终返回相同的结果甚至。
你已经走进了一个人设置的陷阱，他认为伪随机数发生器（PRNG）与密钥导出函数（KDF）是一样的。总的来说，它们的运作非常接近。唯一的问题是，通过（某些实现）Android的加密提供程序实现，setSeed方法将种子添加到随机中，即使它是第一次调用。因此，您每次都会生成一个不同的密钥。不同的密钥意味着可能永远不会被解密的随机密文。
随机密文意味着填充很可能是不正确的，因为使用错误密钥的ECB或CBC解密仍会返回明文 - 它就像密文一样随机。 unpadding例程可能在随机明文上失败，因此解密将失败并出现填充异常。请注意，如果使用了错误的密钥，则经过身份验证的密码（如GCM模式加密）始终会失败。
解决方案：使用真正的随机AES密钥，或使用内置PBKDF2功能从密码（和盐）派生密钥。您可以查看如何执行此操作的示例here。
将SecureRandom用于密钥派生函数的问题：
SecureRandom算法可能（并且确实）每个提供者/运行时不同; SecureRandom实现可能不同; SecureRandom实施可能会在第一次调用SecureRandom期间添加或替换种子; 最后，当使用"SHA1PRNG"时，一些提供程序返回完全不同的随机数生成器，因为默认情况下许多人似乎都这样做。创建随机数生成器时，只需使用new SecureRandom，并记住"SHA1PRNG"不表示特定算法。
使用提供程序，我指的是加密服务提供程序，如Java密码体系结构JCA中所述;即java.security.Provider。
答案 1 :(得分：0)