Hash Function

Hash functions are mathematical operations that take inputs from a string of characters and turn them into an integer. This integer value can then be used as the key for storing information on databases or even saving passwords in a secure way. It is often done in order to search quickly for similar inputs when needed, and this makes it perfect for places like git where many developers work on the same code base at once.

How Does Hash Function Work?

During the process of hashing, it is important to understand what the input and output is for a hash function. The input of a hash function is like a password or some sort of value that you are trying to secure. The output is used to represent this value in an unencrypted way that can later be referenced using the same output value as the key.

Before we can use the output of a hash function as the key for our data, we first need to convert it into something that we can store for future use. This is done by taking the hash function output and encoding it into a unique string that has the same length as the original input (done with a technique called binary encoding).

Now that we have a string, we are ready to convert it into the key. 

This is done by: 

• Taking the hash function
• Applying it to each character one at a time to find the integer that is closest
• Converting all of them into lowercase
• Converting the last character back into uppercase so that we can have some sort of order for our keys

Normally, this is done by taking a piece of data from the string (the output) and finding a new number in the range 0–255, which has been previously generated with some randomness. This number could be called a seed for something else like data, which might help to make some sort of attack against your system more difficult.

Properties of Hash Functions:

• Very fast counting (almost always)
• One way; it cannot be undone
• Output does not display information in the input
• Hard to detect conflict (separate data with the same hash)
• Utilization is based on the performance of a bit of equal storage (XOR and ADD), duplicate, or split

Hash functions are one of those functions that have a million practical uses –  from finding duplicates in large databases to storing passwords securely on computers to encrypting and decrypting messages with cryptography.

Hashing has many practical uses. For example, on the Internet, the SHA-1 hash function is used to verify the integrity of downloaded files. When you download a file from a website such as download.com, they can provide you with an SHA-1 hash value of the file. You can then run this hash value through an online SHA-1 calculator like the one provided by Wolfram Alpha, and it will give you the original file’s exact size in bytes and its CRC32 checksum (hash value) as well.

It is much easier to verify the integrity of a file when you are dealing with a small amount of data, like a hash function can do. For example, if someone had tampered with a file that was 1 MB in size, it would make it significantly harder to detect the tampering because you wouldn’t know the exact value of any change that was made. When you download a 5-MB PDF document from the Internet, there is no way for you to know whether that document has been tampered with without checking it against an online SHA-1 calculator. (However, an online SHA-1 calculator doesn’t let you check anything except the hash value.)

When you run a file through an SHA-1 calculator, it will tell you the size in bytes of the CRC32 checksum of that file. Then you can download the file again and check it against the SHA-1 hash value. If they match exactly except for only a few bytes, then you know that your downloaded file is identical to the original and not tampered with in any way.

How Hashing Works

We store data on key types of keys and values in the hash tables. The input to the hashing function is provided as the key, which is used to identify data. The hash code will map with the default value.

Hash tables should support three operations.

1. Insert 
2. Search 
3. Delete 

Let us take an example to understand this concept, let’s say we want to make a key list of characters for a unit of value unit characters, for example, a map of countries in major cities.

Conclusion

A hash function is a mathematical operation that takes pieces of data and scrambles them up into a smaller, fixed-size value. This operation makes it simple to look up the original input data by comparing it to the stored result of the hash function.