– cryptography public and private key one-way hash function –
We know that in addition to the authenticity of information on the Internet, there is a big problem that users have insufficient motivation to generate incremental data. This is the case when the message board mentioned in the previous article lacks valid data.
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For example, we now have a lot of online lending platforms. When users use their services, they fill in the necessary gender, age, income and other data. If the platform also wants to obtain more auxiliary data items for credit evaluation, users often Not willing to provide.
Some platforms use incentives such as lotteries, rebates, etc. to drive the collection (incentives) of these extra data, or to perform very informative explanations (coordinating expectations), but this is not very effective – some are not sensitive to privacy, or Except for price-first customers. The reason is that there is no reliable encryption technology, users can not fully trust the platform, so even with the promise of incentives, for security reasons, many people are still unwilling to cooperate with the provision of such data.
After combining with encryption technology, the method of stimulating and coordinating expectations can really promote the production and flow of data. Since data ownership is not threatened by the platform side, and the contributions generated can be traced to individuals, users can be more confident in providing incentives by providing data. Imagine that in the scenario of online lending, the process changes to the additional data generated by the user alone. Each time the demand for loan analysis requires the user to provide a special signature authorization, and then the revenue generated by the data use is divided back…
In this case, collaboration in the digital world will be easier to achieve. With the development of individual encryption technology, it will greatly promote the enthusiasm of users to participate deeply and expand the data boundary of our current society. The construction of this new encryption structure will also help humans break through the main bottlenecks currently encountered by big data and AI technologies, that is, multi-dimensional real and reliable data sources, which will become a necessary condition for their next round of rapid growth.
Behind the non-tamperable and cryptographic technologies is cryptography. To illustrate this more clearly, let's take a look at this subject. Because the details of cryptography are too difficult and complicated, involving a large number of mathematical formulas and logical derivations, especially in combination with modern computer networks, quantum and other technologies, it has become increasingly complicated and concealed. So here we can only discuss some of its basic principles and highlight the link between it and the blockchain.
Many of us have seen some cases involving passwords in the history of war. For example, in the battle between the ancient Greek city-states, the letters were transmitted between the two battlefields. In order to worry about the strategic intentions of the enemy after being intercepted, the content of the letter is often written with a set of confidential rules agreed by both parties. In World War II, the Allies also achieved the famous Normandy landing by deciphering the enemy's password. In fact, many advances in cryptography have come from the push of war.
In the age of the Internet, cryptography has become important in business practice for the sake of information security. In the information society, even if others copy our secret information, we are hard to notice because the information on hand is not lost. Because digital documents are easily modified, our important files are at risk of being tampered with by others. In addition, if someone sends our secret information to a third party via email or publicly posted on a social networking site, it will cause us a lot of trouble.
In order to solve the above problems, we have developed a variety of computer network-based cryptography, which is the root of modern cryptography. Essentially, it is a secure wind control technology that we developed to prevent uncontrolled, stolen, or diffused network information. In order to get a general idea of the whole picture of cryptography, we need to know something called a "cryptographer's toolbox."
Among the various types of cryptography, six play a particularly important role. We refer to these types of technologies as ciphers' toolboxes : symmetric ciphers; public key cryptography; one-way hash functions ( Hash function); message authentication code; digital signature; pseudo-random number generator.
The above statement is from Bruce Schnell's "The Truth of Network Information Security". We can use the above diagram to illustrate their role in the information world. Speaking of this, those of us who have an understanding of the blockchain should be able to find some of the words that we often encounter recently, and let us explain them separately.
The first tool is symmetric cryptography, which is simply a shared-key cipher. In this case, the cipher and the decryptor use the same key. The risk in this way is that the key distribution problem needs to be solved. This is like the file encryption password is 123456, the decryptor needs to open the file, you need to know this information, but how can the decryptor know that the password is 123456 in an absolutely safe state?
Although it is possible to exchange information by prior knowledge, such as two people agreeing to a meeting place, or by assigning a key distribution center to inform each other, and adopting a more complicated method like Diffie-Hellman key exchange, there are certain The problem. Cryptology experts have invented a technique for resolving key distribution problems with public key cryptography, which is commonly known as asymmetric ciphers.
This is the second tool public key cryptography, which divides the key into an encryption key and a decryption key. The encryption key is generally public, so the key is called a public key; in contrast, the decryption key is absolutely unpublishable and can only be used by you, so it is called a private key.
In public key cryptography, the user needs to generate a key pair including a public key and a private key, wherein the public key is sent to others for encrypting the information, and the recipient can decrypt only by using the matching private key. information. Since the public key delivered to the other party is public, it does not matter even if it is stolen in the process, which solves the problem of key distribution in the symmetric password.
After the emergence of public key ciphers, it is widely used in various types of information encryption. We can also build cryptosystems that cannot be implemented by many symmetric cryptography technologies, such as generating decentralized identity accounts and digital signature technologies. This will be discussed in detail in a later article.
The third tool is a one-way hash function that has an input value and an output value, where the input is called a message and the output is called a hash value (transliterated to a hash value). The one-way hash function can calculate the hash value based on the content of the message, and the hash value is also used to check the integrity of the message. By using this function, even if you are confirming the integrity of a file of several hundred MB in size, you can compare a short hash value.
In case investigation, the case handler will use the fingerprint. By comparing the fingerprint of a particular person with the fingerprint left by the crime scene, you can know if the task is associated with the case. For the information on the computer network, we can also use a similar "fingerprint". When we need to compare the two information, we don't have to completely compare the contents of the message itself, just compare their "fingerprints". A hash value is a fingerprint that reflects the relevance of such information.
The one-way hash function has four main properties. The first is to calculate a fixed-length hash value based on messages of any length, and the second is to be able to quickly calculate the hash value. Again, the message has different hash values. The case where two different messages produce the same hash value is called a collision. The nature of collisions is called collision resistance, and the one-way hash function used in cryptography requires collision resistance. Finally, there must be unidirectionality, which means that the nature of the message cannot be calculated by hashing.
The one-way hash function is a very central part of cryptography, and we can use it to confirm whether the software we downloaded has been tampered with. For example, many Internet software now publish the hash value calculated by the one-way hash function on the official website. After the user downloads the software to different channels, the user can calculate the hash value and then the hash value published on the official website. Compare.
By hashing the value, the user can confirm that the file they downloaded is consistent with the file provided by the software author . In addition, this function is also required in the process of constructing message authentication codes, digital signatures, and pseudo-random number generators. By using a one-way hash function in the encryption scenario, computer processing time can be saved, and the unpredictability of generated information and the like can be guaranteed.
* The article is the original independent view of the author Li Kailong. Unauthorized reproduction is prohibited.
* Li Kailong, founder and CEO of Digital Agency.