DES加密遇到的问题(Java)

AWP2020

已于 2022-05-04 22:41:19 修改

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分类专栏：学海无涯文章标签： java eclipse

于 2022-04-27 18:46:06 首次发布

本文链接：https://blog.youkuaiyun.com/AWP2020/article/details/124457660

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本文探讨了在Java中使用DES进行解密时遇到的BadPaddingException，通过案例分析了代码错误和修复过程，重点在于理解解密模式选择的重要性。作者揭示了将加密模式用于解密的错误，并给出了正确的CipherOutputStream使用方式。

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错误：java.io.IOException: javax.crypto.BadPaddingException: Given final block not properly padded.

一开始以为是下面这段代码的问题，换成另一段代码。

SecureRandom ran = new SecureRandom();
DESKeySpec dKey = new DESKeySpec(password.getBytes());
SecretKeyFactory kF = SecretKeyFactory.getInstance("DES");
SecretKey skey = kF.generateSecret(dKey);

SecureRandom ran = SecureRandom.getInstance("SHA1PRNG");
ran.setSeed(password.getBytes());
KeyGenerator kgen = KeyGenerator.getInstance("DES");
kgen.init(56,ran);
SecretKey skey = kgen.generateKey();

结果发现问题没有解决。问题在下面这段代码：

Cipher cipher = Cipher.getInstance("DES");
cipher.init(Cipher.DECRYPT_MODE, skey, ran);
byte[] buffer = new byte[1024];
InputStream in = new FileInputStream(file);
OutputStream out = new FileOutputStream(destFile);
CipherInputStream cin = new CipherIntputStream(in,cipher);
int r = 0;
while ((r = in.read(buffer))!=-1) {
      cin.write(buffer, 0, r);
}

改正之后的代码：

Cipher cipher = Cipher.getInstance("DES");
cipher.init(Cipher.DECRYPT_MODE, skey, ran);
byte[] buffer = new byte[1024];
InputStream in = new FileInputStream(file);
OutputStream out = new FileOutputStream(destFile);
CipherOutputStream cot = new CipherOutputStream(out,cipher);
int r = 0;
while ((r = in.read(buffer))!=-1) {
      cot.write(buffer, 0, r);
}