Cracking 40-bit MD5 Encryption

Source: Internet
Author: User

Comments: Generally, the password of the website background administrator is encrypted by MD5, which is about 16-bit and 32-bit. If the password is encrypted by 40-bit for the first time, it is actually the same. 7a57a5a743894a0e4a801fc343894a0e4a801fc3 the original text is admin, which is actually MD5 encryption, but some changes have been made: the first 16 digits, 7a57a5a7438 generally, the website administrator password is encrypted by MD5, almost all are 16-bit and 32-bit,
If we encounter a 40-bit encryption for the first time, it is actually the same.
7a57a5a743894a0e4a801fc343894a0e4a801fc3 admin
This is actually MD5 encryption, but some changes have been made:
The first 16 bits, 7a57a5a743894a0e, are admin's 16-bit MD5 ciphertext; the last 24 bits, note that there is a 43894a0e between two 4a801fc3, 4a801fc3 is the last 8 bits of the 32-bit MD5 ciphertext, while 43894a0e is the last 8 bits of the 16-bit MD5 ciphertext.
Therefore, the ciphertext can be viewed as follows: First encrypt admin with 16-bit MD5, then add the last 8 digits of 32-bit MD5 ciphertext, and finally add the last 16-bit ciphertext (43894a0e4a801fc3) to repeat, 40-bit MD5 encrypted ciphertext is generated.
After knowing the principle, we can see that the last 32-bit ciphertext is actually a 16-bit ciphertext repeat encrypted ciphertext. We can simply take the first 16 digits out to crack the ciphertext, and all the subsequent values are useless.
The benefits of such encryption are self-evident: people generally think that MD5 only has 16-bit and 32-bit encryption methods, although it looks like MD5, however, because the number of digits is different, online and tools cannot be used for cracking. This is another encryption method, and the goal of audio-visual recognition is achieved.
With admin's 16-bit and 32-bit ciphertext:
7a57a5a743894a0e
21232f297a57a5a743894a0e4a801fc3

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