On this occasion, I will complete the homework given by professor @pelon53 which is discussing Hash and Cryptography.

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Explain what does the resistance to collision mean? And what does resistance to preimage mean?

1. Resistance to Collision

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Hash is intended to eliminate a problem in the blockchain network system, namely the collision between each output created. Each output generated by the blockchain must have different characteristics so that every transaction that occurs will not have the same code which will result in a collision between these transactions.

With this problem, a program was created that will create a unique code for each output of transactions that occur on the blockchain, this program is Hash. Hash will use a mathematical algorithm to ensure that each output of different code will have a different code, thus avoiding collisions between transactions that occur.

2. Resistance to Preimage

Preimage resistance is an act of hashing to ensure the data of each block created will remain secure and not easy to hack. Hackers are always looking for checks so that they can attack the blockchain system from the created hash code, they will code that has the same output, then with that code they will get information from the input that should have been hidden.

There are two types of resistance to preimage, including:

• Preimage resistance
• Second preimage resistance

1. Preimage Resistance
Preimage resistance is an action to secure data from every input and output that has the same code, this is made because we must know that there is no perfect system, just like blockchain in creating hash codes sometimes there is an error where the output code generated is the same as the input , to ensure the existing data remains safe, the hash uses preimage resistance.

2. Second preimage resistance
While the second preimage resistance is an action to create a unique output code so that it will be very difficult to find two identical codes between the input and output.

Use tronscan and Etherscan to verify the hash of the last block and the hash of that transaction

1. Tronscan

• First we visit the website of Tronscan (https://tronscan.org/#/) and we will see the initial display of the page which looks like the image below.

• Then if we look at the bottom left of the page we will see a list of blocks made on the Tron blockchain, to see the last block created we just have to select the top block.

• After that we will be taken to another page that contains the details of the block we clicked on, it shows Block Height: 31781998 and Block Hash: 0000000001e4f46e0831eeb0e5bd88d70ad8fbc911d7e5822f3eb3e313096067.

• Meanwhile, to see the last transaction that occurred, we just need to go back to the previous page and then look at the transaction column next to the blocks column earlier. We just need to select the top transaction in that column.

• Then we will be taken to another page that contains the details of the transaction. We can see in the image below that the Block Hash of the transaction is: 2530479d7feb4b16856a116b6fe82579ccbc8925c7e28d4ede940cd05a2b761b.

2. Etherscan

• To see the last block and transaction on the Ethereum Blockchain, we must first visit the website of Etherscan (https://etherscan.io/) and we will see the initial page display which looks like the image below.

• Then if we look at the bottom left of the page we will see a list of blocks made on the Ethereum blockchain, to see the last block created we just have to select the top block.

• After that we will be taken to another page that contains details of the block that we clicked earlier, it shows Block Height: 12792193.

• To see the Block Hash, we just need to scroll down on the page, you can see in the picture below that the Block Hash is: 0x580f75b00e64381806e58e71ad0e1637dfebbae28a70a0bd31cf3277998a6809.

• Meanwhile, to see the last transaction that occurred, we just have to go back to the previous page and then look at the transaction column next to the blocks column earlier. We just need to select the top transaction in that column.

• Then we will be taken to another page that contains the details of the transaction. We can see in the image below that the Block Hash of the transaction is: 0x2ef6d9bb3fbe88b5e010a1600efffdcbeb166c3ad3dfed5398c76412c407ae62.

Generate the hash using SHA-256, from the word CryptoAcademy and from cryptoacademy. Do you see any difference between the two words?

Now I will give an example of how to create a hash of 2 different words, namely "CryptoAcademy" and "cryptoacademy" using SHA-256.

The steps are very easy, we just need to visit the website of SHA256 Hash Generator (https://passwordsgenerator.net/sha256-hash-generator/), then we fill in the column that has been provided with the words we want.

As in the example below I filled in the word "CryptoAcademy" then we can see at the bottom of the image a Hash has appeared with the code: D03CA34B258E6E0FD06B2070DDE61B50BD4EEF6161A8EDAA4A420C9AE1BEB7F9.

Then I tried again with the same word but didn't use capital letters at all ("cryptoacademy"), and as you can see the hash code created is very different from the previous Hash code which is: 0592F5DD27DC72E675B2AB9C77487A69FAAF84196597FA052EC099C18EE7C4C5.

We can see from the two examples above that each different input will produce a different output. Even though the difference is very small, namely in capital letters, but with this slight difference it will make the Hash results made will be very different between the two. With this hash, the level of stability and security of the blockchain system will increase because each hash generated from each input will be different from each other.

In your own words explain the difference between hash and cryptography

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Hash and cryptography are components that both exist in the blockchain network and they have differences between the two, including:

Hash	Cryptography
Algorithms are needed in processing data.	Using a method that has a high level of security.
Makes data hard to hack.	Often used for crime.
No password required.	Requires a password for decryption.
Does not require any software to run it.	Requires software to run it.
Have the same long and unique code	Code length varies with each output.

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Conclusion

Hash and cryptography are very important programs on the blockchain network system to make everything related to the smoothness and security of the blockchain run according to what has been programmed. As we know that there must be errors in the entire system, that's why Has and Cryptography are able to minimize these errors on the Blockchain.