18-bit md5 encryption algorithm Decryption Method

Sometimes there will be 18-bit md5, which is currently from the old Y Article management system.
 
At present, there are too many variant MD5 values. Most of them generate 32 bits to capture the nth to nth bits.
 
The logon page of the old Y Article management system is as follows:
 
Adminpwd = Mid (md5 (adminpwd, 32), 4, 18
The 32-bit md5 value is truncated from 3rd bits to 18 bits.
 
For example:
 
89ACFA07F0F5AD91B0980E08A6228791 the plaintext is 820604
In the old ycm system, the 18-bit screenshot is cfa07f0f5ad91b0980.
Cfa07f0f5ad91b0980
89A CFA07F0F5AD91B0980 E08A6228791
In this way, we can intuitively see that,
Take admin888 as an Example



Open the database and you will find that the generated 18-bit md5 Value
 
 
If the generated 32-bit md5 value is changed to 16-bit md5 value, the first 8 bits and the last 8 bits are removed.
 
However, the 18-bit md5 of the old Y Article management system cannot be restored
 
32-bit to 16-bit:
 
32-bit md5: 89ACFA07F0F5AD91B0980E08A6228791
16-bit md5: F0F5AD91B0980E08 old Y article system 18-bit:
32-bit md5: 89ACFA07F0F5AD91B0980E08A6228791
The 18-bit md5 of old Y: cfa07f0f5ad91b0980 cannot be restored to 16-bit md5, which is much better than dedecms.
The only thing that can be cracked is to compare the approximate values of the ciphertext. It should be okay.
At present, it seems that all websites that decrypt md5 have not provided (compare the approximate values of ciphertext), which leads to the current method of intercepting md5.
Relatively safe.
I can only hope that the function of decrypting md5 and other websites can be improved to provide ciphertext approximate value comparison.

Author: http://www.chouwazi.com/article.asp? Id = 417
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