Hash

Hash (Hash Function) — is a mathematical function that processes the input deck of random length into the output bit line of the established length, performed by a certain algorithm. The initial data is called the input array or message. 

Hash is always unique for each array of information. With the smallest change in the input information, the hash completely changes. The hash function is irreversible and doesn’t allow restoring the original array of information from the character string. This can be done only by sorting through all possible options, which with an endless amount of data requires a lot of time and money.

How Hash works

The cryptographic hash function works in several steps. Data is divided into parts and passed through a compressive function that transforms information into a smaller number of bits. The function should be crypto-resistant with a result that is almost impossible to open. As for the sample functions for more simple cases, it doesn't have to be cryptographic. There, transformations can be easier.

Hashing allows you to quickly calculate the necessary hash for a quite large amount of information. Usually, the algorithm of the hash function is opened to let everyone evaluate its resistance to restoring the initial data on the issued hash. The hash function should be able to bring any amount of data to the number of a given length.

The purpose of hashes is to ensure the user’s safety. Identification or testing of data authenticity is needed to protect sensitive information. That’s why experts use precisely cryptographic hash functions.

Features of Hash

The hash function has several key features that distinguish it from others. The presence of these features is obligatory to make the hashing process complete. 

Features of Hash Function:

Irreversibility. No one can get the initial data from the hash, even theoretically. Too much information is discarded in the process, this isn’t encryption of information.

Determinacy. If you submit the hash function to the same data, then their hash will be the same. It is the feature that allows you to use hashes to verify the authenticity of the information.

Uniqueness. An ideal hash function gives a 100% unique result for each possible set of data. In reality, this is impossible, and sometimes collisions happen. Collision is the appearance of the same hashes for two different input elements. The existing hash functions are quite complicated, so the probability of collisions is minimized.

Diversity. Even if the two sets of information differ in one or two symbols, their hashes will be completely different. They won’t have common blocks, it will be impossible to understand that the initial data are similar.

High generation rate. This is a feature of any hash: unlike encrypted file versions, they are generated quickly, even if the input array is large.

Safety of Hash

There are several criteria the hash has to meet to be considered ideal. Nowadays, no one can satisfy them 100%. That’s why the task of the developers is to create the hash that will be maximally secure. 

Criteria of ideal Hash:

Collision resistance. Collision is an unsafe situation because it allows the computer trespasser to replace the correct information with the false one. The modern cryptographic hash functions aren’t fully collision-resistant. But they are very difficult, and the collision search may take years or ages. It becomes practically impossible to find the collision.

Data recovery resistance. Data recovery resistance means the impossibility to select the possible combination to get the initial array of information. This requirement is fulfilled for modern functions. There is so much information in the world that the complete overcoming of all possible combinations would take an infinitely large amount of time.

Application of Hash

Today the hash function is applied in many spheres. Usually, they are related to digital safety, data protection, and cryptocurrencies. 

Spheres of Hash application: 

Data integrity check during transmission. This function is related to the data check. For example, one user transmits a data array to another and then gives a hash. The recipient gets the information, compares the hashes, and ensures that they have received the necessary data.

Also, the data integrity check is used in blockchain. Hash provides the integrity of the payments and protects them from unauthorized changes. That’s why it is difficult to hack a blockchain. 

Electronic signatures. The use of hash in this technology allows the user signing the document to be sure that they sign exactly the required document. Hash is also applied in the formation of electronic signatures and encryption.

Registration and authorization. During the registration of a personal account, the password and other data of the user are processed via hashing. Then, it is placed in the database. At the next entrance, this data will be processed again, and the hash function will compare the introduced option with the previously added variant. Without this function, such a process would be too long.