为什么TripleDES.Create（），关键不是这个算法有效的大小？ [英] Why the TripleDES.Create().Key is not a valid size for this algorithm?

问题描述

在我需要解密用不同势键
I文本还需要genreate在后面的代码有效密钥的情况下。

我用这条线来产生。一键

  VAR键= Encoding.UTF8.GetString（TripleDES.Create（）键。）; 
  

但不能使用这种方法的关键。它说：指定的密钥不是这个算法有效大小

如何解决这种情况呢？

 公共类CryptoHelper 
 {
公共字符串加密（字符串toEncrypt，串键）
 {
 VAR toEncryptArray = Encoding.UTF8.GetBytes（ toEncrypt）; 
 VAR keyArray = Encoding.UTF8.GetBytes（键）; 
 
变种TDES =新TripleDESCryptoServiceProvider {重点= keyArray，模式= CipherMode.ECB，填充= PaddingMode.PKCS7}; 
 
 VAR cTransform = tdes.CreateEncryptor（）; 
变种resultArray = cTransform.TransformFinalBlock（toEncryptArray，0，toEncryptArray.Length）; 
 tdes.Clear（）; 
 
返回Convert.ToBase64String（resultArray，0，resultArray.Length）; 
} 
 
公共字符串解密（字符串cipherString，串键）
 {
 VAR toEncryptArray = Convert.FromBase64String（cipherString.Replace（''，'+'） ）; 
 VAR keyArray = Encoding.UTF8.GetBytes（键）; 
变种TDES =新TripleDESCryptoServiceProvider {重点= keyArray，模式= CipherMode.ECB，填充= PaddingMode.PKCS7}; 
 
 VAR cTransform = tdes.CreateDecryptor（）; 
变种resultArray = cTransform.TransformFinalBlock（toEncryptArray，0，toEncryptArray.Length）; 
 tdes.Clear（）; 
 
返回Encoding.UTF8.GetString（resultArray）; 
} 
} 
  

解决方案

如果你写一个小测试，你的问题变得很明显，

  VAR失败= ParallelEnumerable.Range（0，10000）.Count之间（我= GT; 
 {
 VAR keyBefore = TripleDES.Create（）键; 
 VAR keyAfter = Encoding.UTF8.GetBytes（Encoding.UTF8.GetString（keyBefore））; 
返回keyBefore.SequenceEqual（keyAfter）;！
}）; 
  

在我的测试中，每一个试图往返失败。这证实了达明的评论。

有这么一个按键可以安全所产生的字节并不保证
轮，奔进一个字符串通过充当如果他们是一个合法的UTF-8
序列。

的

keyAfter （几乎）总是有所扩大，有时一倍的长度。事实上，我无法侥幸的键是圆形trippable，这可能是与避免弱密钥。

---

但是，如果我尝试

  VAR失败= ParallelEnumerable.Range（0，10000）.Count之间（I => 
 {
 VAR keyBefore = TripleDES.Create（）键; 
 VAR keyAfter = Convert.FromBase64String（Convert.ToBase64String（keyBefore））;！
返回keyBefore.SequenceEqual（keyAfter ）; 
}）; 
  

失败总是等于 0 ，符合市场预期。所以，有一个简单的解决方案。

in a case i need to decrypt texts with diffrent keys i also need to genreate valid keys in code behind.

i am using this line to generate a key.

var key = Encoding.UTF8.GetString(TripleDES.Create().Key);

but can't use that key in this method. it says "Specified key is not a valid size for this algorithm"

how can i fix this situation?

public class CryptoHelper
{
    public string Encrypt(string toEncrypt, string key)
    {
        var toEncryptArray = Encoding.UTF8.GetBytes(toEncrypt);
        var keyArray = Encoding.UTF8.GetBytes(key);

        var tdes = new TripleDESCryptoServiceProvider { Key = keyArray, Mode = CipherMode.ECB, Padding = PaddingMode.PKCS7 };

        var cTransform = tdes.CreateEncryptor();
        var resultArray = cTransform.TransformFinalBlock(toEncryptArray, 0, toEncryptArray.Length);
        tdes.Clear();

        return Convert.ToBase64String(resultArray, 0, resultArray.Length);
    }

    public string Decrypt(string cipherString, string key)
    {
        var toEncryptArray = Convert.FromBase64String(cipherString.Replace(' ', '+'));
        var keyArray = Encoding.UTF8.GetBytes(key);
        var tdes = new TripleDESCryptoServiceProvider { Key = keyArray, Mode = CipherMode.ECB, Padding = PaddingMode.PKCS7 };

        var cTransform = tdes.CreateDecryptor();
        var resultArray = cTransform.TransformFinalBlock(toEncryptArray, 0, toEncryptArray.Length);
        tdes.Clear();

        return Encoding.UTF8.GetString(resultArray);
    }
}

解决方案

If you write a little test, your problem becomes obvious,

var failures = ParallelEnumerable.Range(0, 10000).Count(i =>
    {
        var keyBefore = TripleDES.Create().Key;
        var keyAfter = Encoding.UTF8.GetBytes(Encoding.UTF8.GetString(keyBefore));
        return !keyBefore.SequenceEqual(keyAfter);
    });

In my testing, every attempted roundtrip fails. This confirms Damien's comment.

There's no guarantee that the bytes generated for a key can be safely round-tripped into a string by acting as if they're a valid UTF-8 sequence.

The keyAfter is (almost) always somewhat expanded, sometimes doubled in length. In fact, I'm unable to fluke a key that is round trippable, this may have something to do with avoiding weak keys.

---

However, if i try

var failures = ParallelEnumerable.Range(0, 10000).Count(i =>
    {
        var keyBefore = TripleDES.Create().Key;
        var keyAfter = Convert.FromBase64String(Convert.ToBase64String(keyBefore));
        return !keyBefore.SequenceEqual(keyAfter);
    });

failures always equals 0, as expected. So, there is a simple solution.

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