两种不同的BASE 64 EN codeD字符串可能会导致成相同的字符串，如果去codeD？ [英] Can two different BASE 64 encoded strings result into same string if decoded?

问题描述

在客户端上我做的一个字符串的MD5加密，然后生成散列​​基地64编码。

On client side I am doing an MD5 encryption of a string and then a BASE 64 encoding on the hash generated.

这最终连接codeD的字符串是用于在服务器端进行比较。

This final encoded string is then used for comparison on server side.

我能够为许多测试用例成功地做到这一点，但它失败了下面的一个。

I was able to do this successfully for many test cases but it failed for the below one.

对于字符串的MD5

  2679:07071960:09348448:3:08912206:3:EXPRESS:1:EU4NW31E7INEC1X

我的MD5哈希字符串：

My MD5 hash string:

  291423A531148527A9524EA0924CDF68

我的Base64 EN codeD字符串：

My Base64 encoded string:

  KRQjpTEUhSepUk6gkkzfaA==

当我尝试把对BASE64编码MD5散列串在 HTTP： //www.opinionatedgeek.com/dotnet/tool​​s/base64en$c$c/ 的它生成以下字符串：

When I try to put the MD5 hash string for BASE64 encoding on http://www.opinionatedgeek.com/dotnet/tools/base64encode/ it generates following string:

  MjkxNDIzQTUzMTE0ODUyN0E5NTI0RUEwOTI0Q0RGNjg=

但是，当我尝试去code我Base64编码字符串，那就是KRQjpTEUhSepUk6gkkzfaA ==，这里的 http://www.opinionatedgeek.com/dotnet/tool​​s/Base64De$c$c/Default.aspx 我得到我的哈希code（开在十六进制编辑器生成.bin文件）。

But, when I try to decode my Base64 string, that is "KRQjpTEUhSepUk6gkkzfaA==", here http://www.opinionatedgeek.com/dotnet/tools/Base64Decode/Default.aspx I am getting my Hash Code(opened the .bin file being generated in hex editor).

那么，是有可能，一个字符串可以有多个连接的Base64 codeD值？

So, is it possible that a single string may have multiple Base64 encoded value?

我使用的是低于code产生的EN codeD字符串：

I am using the below code for generating the encoded string:

  public static String getHashCode(String text) 
 { 
    MessageDigest md;
    byte[] md5hash = new byte[32];
    try{
    md = MessageDigest.getInstance("MD5");

    md.update(text.getBytes("iso-8859-1"), 0, text.length());
    md5hash = md.digest();
    }
    catch(Exception e)
    {
        return "-1";
        }
    String encoded = Base64.encode(md5hash);
    String retValue = new String(encoded);


    return retValue;

   } 

请，建议什么错误，以及如何确保我们使用相同的客户端和服务器端都消化

Kindly, suggest what is going wrong and how to make sure that we use same digest both on client and server side.

推荐答案

您有MD5哈希291423A531148527A9524EA0924CDF68生成中的Base64 EN codeD字符串MjkxNDIzQTUzMTE0ODUyN0E5NTI0RUEwOTI0Q0RGNjg =，这是罚款。你已经转换的MD5哈希为ASCII十六进制重新presentation和Base64 EN codeD的。

You have the MD5 Hash 291423A531148527A9524EA0924CDF68 that generates the Base64 encoded string MjkxNDIzQTUzMTE0ODUyN0E5NTI0RUEwOTI0Q0RGNjg= , which is fine. You have converted the MD5 hash to an ascii hex representation, and base64 encoded that.

不过自己getHash code（）的工作方式不同，它创建的二进制的再$ P $您的哈希code的psentation，你有没有转换你的哈希的base64编码一个十六进制ASCII重新presentation，这就是为什么你看到不同的base64 EN codeD字符串。

However your own getHashCode() works differently, it creates a base64 encoding of the binary representation of your hash code, you have not converted your hash to an ascii hex representation, and that's why you see different base64 encoded strings.

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