Md5 description [from 99Bill interface description]

MD5 Algorithm introduction.
The full name of MD5 is message-Digest algorithm 5 (Information-Digest algorithm ).
Developed by Ronald L. Rivest of laboratory for computer science and RSA Data Security Inc
Md2, md3, and md4 are developed. It enables large volumes of information to sign private keys using digital signature software.
Is "COMPRESSED" into a confidential format (that is, to convert a byte string of any length into a large integer of a certain length ). No
Whether it is md2, md4, or MD5, they all need to obtain a random length information and generate a 128-bit message
. Although the structures of these algorithms are more or less similar, the design of md2 is completely different from that of md4 and MD5.
The same is because md2 is designed and optimized for 8-bit machines, while md4 and MD5 are designed for 32-bit computers.
The description of the three algorithms and the C-language source code are described in detail in Internet rfcs 1321.
Http://www.ietf.org/rfc/rfc1321.txt), which is the most authoritative document by Ronald L. Rivest in 1992
Submitted to Ieft on April 9, August.
Rivest developed the md2 Algorithm in 1989. In this algorithm, the information is first supplemented to make the information
The length of the byte is a multiple of 16. Then, a 16-bit test and append to the end of the information. And according to this new product
The generated information is used to calculate the hash value. Later, Rogier and chauvaud found that if the test is ignored, the md2 attack will be generated.
Burst. The encrypted result of the MD2 algorithm is unique-there are no duplicates.
To enhance algorithm security, Rivest developed the MD4 Algorithm in 1990. The MD4 algorithm is also required.
Fill in the information to ensure that the length of the byte information can be fully divided by 448 (the length of the byte information mod 512 = 512 ).
Then, the initial length of a 64-bit binary information is added. Information is processed into 512 bits
Damg? Rd/Merkle iteration structure blocks, and each block must be processed in three different steps. Den Boer and
Bosselers and others quickly discovered the first and third vulnerabilities in the attack MD4. Dobbertin Orientation
We demonstrated how to use a normal PC to find conflicts in the full version of MD4 in a matter of minutes.
It is actually a vulnerability that may encrypt different contents but may get the same encrypted result ). No
No doubt, MD4 is eliminated.
Although the MD4 algorithm has such a large vulnerability in security, it has several types of information developed only after it is developed.
The emergence of security encryption algorithms has a guiding role that cannot be ignored. In addition to MD5, the most famous ones are:
SHA-1, RIPE-MD and HAVAL.
One year later, in 1991, Rivest developed a more sophisticated MD5 algorithm. In
Added the concept of "Safety-strap" (Safety-Belts. Although MD5 is a little slower than MD4
For security. This algorithm is obviously composed of four and MD4 designs with a few different steps. In the MD5 algorithm,
Information-the size and filling conditions of the summary are identical to those of md4. Den Boer and bosseloers once found MD5
Pseudo-Collisions in the algorithm, but no other encrypted results are found.
Van Oorschot and winne have considered a function for Brute Force search conflict in the Hash (Brute-Force Hash ).
And they guess a machine designed specifically to search for MD5 conflicts (this machine was created in 1994 ).
The manufacturing cost is about $1 million), and a conflict can be found every 24 days on average. However, from 1991 to 2001
In the past 10 years, there has not been any replacement for MD6 or new algorithms named by other names,
We can see that this flaw does not significantly affect the MD5 security. None of the above is enough
MD5 problems in practical application. In addition, because the MD5 algorithm does not need to pay any copyright fee,
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Therefore, in general cases (non-top secret application fields. However, even in the secret field, MD5 is also
Very good Intermediate Technology), MD5 should be considered very safe.