我正在使用教程中的这个简单类来加密我的 Android 应用程序中的字符串并在 Java REST 后端对其进行解密:
package classes;
import java.security.NoSuchAlgorithmException;
import javax.crypto.Cipher;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
public class MCrypt {
private String iv = "fedcba9876543210";
private IvParameterSpec ivspec;
private SecretKeySpec keyspec;
private Cipher cipher;
private String SecretKey = "0123456789abcdef";
public MCrypt()
{
ivspec = new IvParameterSpec(iv.getBytes());
keyspec = new SecretKeySpec(SecretKey.getBytes(), "AES");
try {
cipher = Cipher.getInstance("AES/CBC/NoPadding");
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
} catch (NoSuchPaddingException e) {
e.printStackTrace();
}
}
public String encrypt(String text) throws Exception
{
if(text == null || text.length() == 0)
throw new Exception("Empty string");
byte[] encrypted = null;
try {
cipher.init(Cipher.ENCRYPT_MODE, keyspec, ivspec);
encrypted = cipher.doFinal(padString(text).getBytes());
} catch (Exception e)
{
throw new Exception("[encrypt] " + e.getMessage());
}
return bytesToHex(encrypted);
}
public String decrypt(String code) throws Exception
{
if(code == null || code.length() == 0)
throw new Exception("Empty string");
byte[] decrypted = null;
try {
cipher.init(Cipher.DECRYPT_MODE, keyspec, ivspec);
decrypted = cipher.doFinal(hexToBytes(code));
} catch (Exception e)
{
System.out.println(e.toString());
}
return new String(decrypted);
}
public static String bytesToHex(byte[] data)
{
if (data==null)
{
return null;
}
int len = data.length;
String str = "";
for (int i=0; i<len; i++) {
if ((data[i]&0xFF)<16)
str = str + "0" + java.lang.Integer.toHexString(data[i]&0xFF);
else
str = str + java.lang.Integer.toHexString(data[i]&0xFF);
}
return str;
}
public static byte[] hexToBytes(String str) {
if (str==null) {
return null;
} else if (str.length() < 2) {
return null;
} else {
int len = str.length() / 2;
byte[] buffer = new byte[len];
for (int i=0; i<len; i++) {
buffer[i] = (byte) Integer.parseInt(str.substring(i*2,i*2+2),16);
}
return buffer;
}
}
private static String padString(String source)
{
char paddingChar = ' ';
int size = 16;
int x = source.length() % size;
int padLength = size - x;
for (int i = 0; i < padLength; i++)
{
source += paddingChar;
}
return source;
}
}
它可以很好地解密我的字符串。当我发送一个我篡改过的加密字符串(替换加密字符串中的一个字符,在解密方法中作为“字符串代码”的那个),当我尝试转换字节时出现异常(NumberFormatException)[]到一个字符串。
我对密码学完全陌生,知道我需要学习基础知识。
我想知道的是:这是检查加密字符串是否有效的常用方法吗?没有可以预先检查的布尔方法吗?如果我保持这样,抛出异常会对我的后端服务的性能产生负面影响吗?
编辑:继承堆栈跟踪:
java.lang.NumberFormatException: For input string: "zf"
java.lang.NullPointerException
at java.lang.String.<init>(String.java:601)
at classes.MCrypt.decrypt(MCrypt.java:71)
at service.Service.cryptotest(Service.java:340)
at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:616)
at us.antera.t5restfulws.services.impl.RestfulWSDispatcher.invokeMethod(RestfulWSDispatcher.java:133)
at us.antera.t5restfulws.services.impl.RestfulWSDispatcher.service(RestfulWSDispatcher.java:76)
at $RequestHandler_15b88bc6f1e4.service(Unknown Source)
at $RequestHandler_15b88bc6f1d7.service(Unknown Source)
at org.apache.tapestry5.services.TapestryModule$HttpServletRequestHandlerTerminator.service(TapestryModule.java:253)
at org.apache.tapestry5.internal.gzip.GZipFilter.service(GZipFilter.java:53)
at $HttpServletRequestHandler_15b88bc6f1d9.service(Unknown Source)
at org.apache.tapestry5.internal.services.IgnoredPathsFilter.service(IgnoredPathsFilter.java:62)
at $HttpServletRequestFilter_15b88bc6f1d5.service(Unknown Source)
at $HttpServletRequestHandler_15b88bc6f1d9.service(Unknown Source)
at org.apache.tapestry5.services.TapestryModule$1.service(TapestryModule.java:852)
at $HttpServletRequestHandler_15b88bc6f1d9.service(Unknown Source)
at $HttpServletRequestHandler_15b88bc6f1d4.service(Unknown Source)
at org.apache.tapestry5.TapestryFilter.doFilter(TapestryFilter.java:171)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1212)
at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:399)
at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:766)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:450)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at org.mortbay.jetty.Server.handle(Server.java:326)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:928)
at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:549)
at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:212)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:410)
at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)
编辑:好的,显然我在“测试场景”中犯了一些新手错误;)。我用一个有效的 16 位十六进制字符串尝试了相同的调用,结果decrypt
是一些看起来很奇怪的字符串,这是我所期望的。因此,我将首先检查传入的加密字符串是否是有效的十六进制,然后将其发送到解密方法,然后检查解密的字符串是否包含我期望它包含的内容。非常感谢大家:)