javax.crypto.BadPaddingException
javax.crypto.BadPaddingException
提问于 2011-01-02 22:59:01
我正在研究AES算法，我有一个我无法解决的异常。
javax.crypto.BadPaddingException: Given final block not properly padded
at com.sun.crypto.provider.SunJCE_f.b(DashoA13*..)
at com.sun.crypto.provider.SunJCE_f.b(DashoA13*..)
at com.sun.crypto.provider.AESCipher.engineDoFinal(DashoA13*..)
at javax.crypto.Cipher.doFinal(DashoA13*..)异常发生在解密部分。我在与解密算法不同的地方初始化密钥。
KeyGenerator kgen = KeyGenerator.getInstance("AES");//key generation for AES
kgen.init(128); // 192 and 256 bits may not be available然后，我将它与我从文件中读取的密码文本传递给以下方法
public String decrypt(String message, SecretKey skey) {
byte[] raw = skey.getEncoded();
SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
// Instantiate the cipher
Cipher cipher;
byte[] original = null;
try {
cipher = Cipher.getInstance("AES");
cipher.init(Cipher.DECRYPT_MODE, skeySpec);
System.out.println("Original string: "
+ message);
original = cipher.doFinal(message.trim().getBytes()); //here where I got the exception
String originalString = new String(original);
}
//catches编辑这里是加密方法。
public String encrypt(String message, SecretKey skey) {
byte[] raw = skey.getEncoded();
SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
// Instantiate the cipher
Cipher cipher;
byte[] encrypted = null;
try {
cipher = Cipher.getInstance("AES");
cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
encrypted = cipher.doFinal(message.getBytes());
System.out.println("raw is " + encrypted);
} catches
return asHex(encrypted);
}这是asHex方法
public static String asHex(byte buf[]) {
StringBuffer strbuf = new StringBuffer(buf.length * 2);
int i;
for (i = 0; i < buf.length; i++) {
if (((int) buf[i] & 0xff) < 0x10) {
strbuf.append("0");
}
strbuf.append(Long.toString((int) buf[i] & 0xff, 16));
}
return strbuf.toString();
}这里是我从文件中读取密码文本的地方
static public String readFile(String filePath) {
StringBuilder file = new StringBuilder();
String line = null;
try {
FileReader reader = new FileReader(filePath);
BufferedReader br = new BufferedReader(reader);
if (br != null) {
line = br.readLine();
while (line != null) {
file.append(line);
// System.out.println("line is " + line);
line = br.readLine();
}
}
br.close();
reader.close();
} catch (IOException ex) {
Logger.getLogger(FileManagement.class.getName()).log(Level.SEVERE, null, ex);
}
System.out.println("line is " + file.toString());
return String.valueOf(file);
}有人能帮忙吗？
回答 4
Stack Overflow用户
发布于 2012-01-04 08:29:44
我确实有一个坏的填充例外，没有能够在互联网上找到解决我的问题的办法。因为我在辛苦工作了一段时间后发现了它，我就把它放在这里。
我的问题是，我在硬盘上读取一个文件，并通过缓冲区加密它，总是调用doFinal()方法而不是update()方法。所以在解密的时候，我有填充错误
input = new FileInputStream(file);
output = new FileOutputStream(newFile);
Cipher cipher = Cipher.getInstance("DES");
cipher.init(Cipher.ENCRYPT_MODE, mySecretKey);
byte[] buf = new byte[1024];
count = input.read(buf);
while (count >= 0) {
output.write(cipher.update(buf, 0, count)); // HERE I WAS DOING doFinal() method
count = input.read(buf);
}
output.write(cipher.doFinal()); // AND I DID NOT HAD THIS LINE BEFORE
output.flush();在解密时，使用相同的方法，但使用DECRYPT_MODE的密码
input = new FileInputStream(file);
output = new FileOutputStream(newFile);
Cipher cipher = Cipher.getInstance("DES");
cipher.init(Cipher.DECRYPT_MODE, mySecretKey);
byte[] buf = new byte[1024];
count = input.read(buf);
while (count >= 0) {
output.write(cipher.update(buf, 0, count)); // HERE I WAS DOING doFinal() method
//AND HERE WAS THE BadPaddingExceotion -- the first pass in the while structure
count = input.read(buf);
}
output.write(cipher.doFinal()); // AND I DID NOT HAD THIS LINE BEFORE
output.flush();在编写了代码之后，我就没有任何BadPaddingException了。
我可以精确地指出，只有当原始的清除文件长度(通过file.length()获得)大于缓冲区时，才会出现此异常。否则，我们不需要在while结构中传递几次，我们可以使用doFinal()调用在一次传递中加密。这将使异常的随机字符与您试图加密的文件大小相一致。
我希望你读得很好！
Stack Overflow用户
发布于 2011-01-02 23:12:38
我猜表达式message.trim().getBytes()不返回加密消息时生成的相同字节。特别是，trim()方法可以删除作为填充添加到加密消息中的字节。
验证加密期间doFinal()方法返回的数组和message.trim().getBytes()返回的数组
- 有相同的字节数(数组长度)
- 在数组
中得到相同的字节
Stack Overflow用户
发布于 2015-01-26 12:42:47
KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
kpg.initialize(512);
KeyPair rsaKeyPair = kpg.genKeyPair();
byte[] txt = "This is a secret message.".getBytes();
System.out.println("Original clear message: " + new String(txt));
// encrypt
Cipher cipher;
try
{
cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
cipher.init(Cipher.ENCRYPT_MODE, rsaKeyPair.getPublic());
txt = cipher.doFinal(txt);
}
catch (Throwable e)
{
e.printStackTrace();
return;
}
System.out.println("Encrypted message: " + new String(txt));
// decrypt
try
{
cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
cipher.init(Cipher.DECRYPT_MODE, rsaKeyPair.getPrivate());
txt = cipher.doFinal(txt);
}
catch (Throwable e)
{
e.printStackTrace();
return;
}
System.out.println("Decrypted message: " + new String(txt));页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/4580982
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