Hash function
Put in simple words, the hash function is part of cryptocurrencies that make Bitcoin possible. A cryptographic hash function is used for Bitcoin mining. It is also known as “Keccak” and is a part of the Ethereum Proof of Work algorithm “Ethash”.
How it all started and how it works
Hash functions are used to secure communication through the internet. The hash function hacks up information and then puts it in a different form. The product that is represented by the hash function is called a “hash”.
It works like that – the hash function checks whether the information, that you received from someone, is complete and if the order is correct.
Secure Hash
The Secure Hash Algorithm or in other words “SHA” is one of the secure hash algorithms in the world. SHA-256 was developed as part of the SHA-2 algorithm by NSA in 2001.
SHA-2 algorithm of NSA has no back doors in the algorithm, that is because it is uncovered and anyone who would like could examine it. If there were a back door, it would be impossible that thousands of cryptographers did not notice them.
A lot of people have critical glances at algorithms, but that is normal because crackers of codes have a high reputation because they test the security of algorithms to the limit.
What does SHA-256 do?
If you put any text file into SHA-256 you get an output of letters and numbers in a total of 64 digits. When you put the same text file in SHA-256 it will always end up the same, same numbers, same letters, and in the same sequence.
Even long files can be hashed. You can use the whole book to hash it, and it still will end up with 64 digits. It doesn’t matter how long your chosen file is because SHA-256 will hash it into only 64 digits.
Each file is structured differently and has a different sequence of zeros and ones unless they are real copies. You can use SHA to test if the file is a copy and give the file a unique hash value. The hash value is also called the “fingerprint” of a file.
No two files may produce the same hash value, in order for files to be unique. If some poets’ work would be hashed, the same hash value must not be used. Identification would not be unique and the hash function would be unusable.
Security
If you enter three letters and get 64 digit hash number when you enter the same three letters, but this time you add one more, the hash value would not be even similar.
When someone wants to check if their file has arrived completely, they need to compare the hash value of the sent file with the hash value of the original file.
It is possible to calculate hash values from keys, but it is not possible to calculate keys from hash values. A good hash function, not to be able to deduce the origin or the “original image” from a hash value, is called “original image resistance.”
It is impossible to try other keys to generate the same hash values. Passwords that are used on the internet are stored as hash values in databases, not in their original form. To gain access to the website, the site checks whether the hash value of the password entered matches the hash value in the database.
The attacker could simply take the hash value from the database and will try to find the right key that generates the exact hash value. To do that attackers have to try two of 256 possible combinations, which is humanly impossible even with modern computers it would take a lifespan of our solar system.
The avalanche effect describes the property that the similarity between input values is no longer present at the output values. There are no conclusions that can be drawn about the original data and even top-secret hashes can be sent around safely.
The Hash function is a very secure way how to protect your data from attackers. If it is impossible to find the right combination of hash values then it is a simply great creation to use for protecting a sensitive file or content that you don’t want others to see.
