![image.png](https://cdn.steemitimages.com/DQmUjW93ZzS8RHdXBAn3xQgxXu7umsP1rA6uh6iTLCK8Pdf/image.png)
[Source](https://d32ijn7u0aqfv4.cloudfront.net/wp/wp-content/uploads/raw/SOIN1021412_780x440_mobile.jpg)


<div class="text-justify">


### Resistance to Collision
Resistance to Collision is one of the terms when it comes to blockchain technology. Resistance to Collision in cryptography terms is the property of a hash function where two colliding inputs come out with the same output and with the same hash. When it comes to resistance to collision, there has to be cryptographic has function as well. Resistance to collision is basically when the hash function becomes difficult for two inputs hashing to the same output. With that said, there will be a collision each time a hash function has more input that it has more output. Hashing is basically the process where an input of varying length passes through a special algorithm to produce an output of a fixed length. In the world of blockchain technology, hashing are a key aspects many blockchain technologies. Simply put, resistance to collision occurs when inputs which are not the same produce the same output. Recently, the hash functions that many blockchain technology make use of are collision resistant so as to prevent two different inputs having the same hash output.

When it comes to resistance to collision, it is impossible for the hash gotten from an input to match another hash that is produced by another input. The SHA-2 (including SHA 224, SHA 256, SHA 384, SHA 512) are hash functions which are considered to be very efficient when it comes to resistance to collision so as to prevent different inputs from having the same output. In this case, whenever a hash function becomes resistance to collision or collision resistant, it is difficult to discover identical outputs which prevents confusion from the original has being unnecessarily swapped for the fake hash. The resistance to collision become very necessary when there is dependent on the hash functions to produce two inputs to two different outputs. As far as cryptographic has function is concerned, resistance to collision is a very important aspect so as to maintain the authenticity of both the inputs and outputs that are unique for the transaction.




### Resistance to Preimage
Resistance to Preimage is yet another very important aspect of the hash function because of how difficult it is for attackers to discover which input matches the output hash, this is why the resistance to preimage is very powerful and a necessity as far as hash function is concerned[.](https://steemit.com/hive-108451/@chimzycash/steemit-crypto-academy-season-3-week-2-post-for-pelon53) With this, no attacker can alter or manipulate the hash of any of the transactions simply because it is impossible to discover the input that of the hash output.  Hence why the preimage is associated to one way functions. When it comes to securing the hash from attackers, the resistance to preimage in the hash function is very important because it helps secure the hash from bad actors who wants to alter or manipulate the hash.

This is a very powerful and important security property that is unique in its own way because any bad actor that aims to alter or manipulate the hash will find it very difficult and almost impossible to discover the matching input from the output. In the resistance to preimage, there is the first preimage resistance and second preimage resistance. The first preimage resistance is characterized as the one way function simply because it is impossible to invert it to generate the inputs that produced the output hash. This is beneficial because it improves the security of the stored data in the hash. Simply put, the input that produced the hash is irreversible. In the second preimage resistance, it is not possible for the output of another input to be the same to the first input. Simply put, it is not possible for a second input to produce identical has as the first input.



</div>