Shulou(Shulou.com)06/01 Report--

Interpretation of Google's algorithm for Breaking Network Security

Give all your friends (whether you know about information security or not, as long as you want to know) about what happened to Google's breach of SHA-1.

(Feng Lichao @ Hanbo Information is original, reproduced, please indicate)

When you publish an article, how do you prove that the article has not been tampered with? :

The computer uses an algorithm (hash algorithm, such as SHA) to calculate the content of the whole article, get a short number string (hash value), encrypt the number string, and send it to each other together with the article (this is called digital signature).

After receiving this article, the other party will do the same operation on it and compare the number string. If it is consistent, it will prove that the article has not been tampered with. Of course, all this is done automatically by the computer, and you don't need to participate.

The hash algorithm ensures that each calculation of the same article gets the same value, while the probability of getting the same value for different articles is extremely low. (1max 9223372036854775808)

The key is that it mathematically ensures that the content of the article cannot be calculated backwards from the hash value. There is no inverse function for this function. So you can take x into the function to calculate y, but you can't calculate x based on the value of y. Do you remember this concept? )

Therefore, if the hash value calculated again by the other party is the same as the hash value you sent with the article, it can prove that the article has not been tampered with.

What Google scientists do this time is to find a way to easily generate another article with the same hash value as one article.

There are two ways, one is to find the problem of hashing algorithm mathematically, which we can confirm is not feasible, and it has been proved to be no problem mathematically.

The second method is called brute force cracking, that is, I try, I always find another article with the same hash value. This is feasible in theory, but in practice, it is far from enough to try and calculate for thousands of years.

What Google has done this time is to find some rules and algorithms, and at the same time, with the help of cloud computing, things that were thought to take thousands of years to crack can be broken overnight. (100,000 times faster than brute force cracking)

In order to ensure information security, the specific details of the algorithm will not be released by Google until 90 days later, so that the field of information security can respond.

The Chinese translation of Google's release of the technology can be found at http://mp.weixin.qq.com/s/07pyiX6LAZxasKRYkBz6KA.

Description:

1. The hashing algorithm is mathematically fine, so Google's response is just to suggest upgrading from SHA-1 to a more complex SHA-256.

two。 This is a popular text written by me (Feng Lichao @ Hanbo Information) to my moments on the high-speed rail, to make sure that all friends who can use Wechat can read it, and not to ensure the rigor of technology and terminology.

3. The article takes "an article" as an example, which can actually be any information, such as web page, bank transaction information, × × bank card chip and so on.

4. Thumb typing is hard, reprint please indicate the source:)

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