我使用加密AES算法,当我加密16字节(一个块),结果是32字节.
这个可以吗？
这个可以吗？
我使用的源代码是：
package net.sf.andhsli.hotspotlogin;
import java.security.SecureRandom;
import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
/**
* Usage:
* <pre>
* String crypto = SimpleCrypto.encrypt(masterpassword,cleartext)
* ...
* String cleartext = SimpleCrypto.decrypt(masterpassword,crypto)
* </pre>
* @author ferenc.hechler
*/
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");
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);
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));
}
}
解决方法
如果你看看
specification section 5,那么你可以看到输入,输出和状态都是128位.唯一不同的是键的大小：128,196或256位.因此加密16字节输入状态将产生16字节的输出状态.
你确定你不是用十六进制符号或类似的长度混合吗？如果是十六进制符号,那么它是正确的,因为每个字节需要两个字符来表示它：00-FF(范围0-255).
验证加密是否正确的另一种方法是通过进行等效解密,查看是否匹配明文输入字符串.
无论如何,它是正确的事情.这是一个测试：
public static void main(String[] args) {
try {
String plaintext = "Hello world",key = "test";
String ciphertext = encrypt(key,plaintext);
String plaintext2 = decrypt(key,ciphertext);
System.out.println("Encrypting '" + plaintext +
"' yields: (" + ciphertext.length() + ") " + ciphertext);
System.out.println("Decrypting it yields: " + plaintext2);
}
catch (Exception ex) {
ex.printStackTrace();
}
}
其中产生：
Encrypting ‘Hello world’ yields: (32)
5B68978D821FCA6022D4B90081F76B4FDecrypting it yields: Hello world
