1.- Explain what does the resistance to collision mean? And what does resistance to preimage mean?
Before explaining Resistance to Collision, and resistance to preimage, it will be good to understand where the phrases come into play. Both phrases come into play with Hash.
Hashes are mathematical functions used to compress messages input of any size into a fixed length of alphanumeric character. In other to confirm that a Hash is cryptographically secure, it is required to have the following properties which are; Resistance to Collision, and Resistance to Preimage.
Resistance to Collision
I will refer to this as the first property that confirms a Hash is cryptographically secured. Collision refers to the process whereby two distinct inputs produce the same result/output/digest. With this, you should have gotten an understanding of what Resistance to Collision means, it is the property of a hash where two different input messages should not hash to the same output.
Resistance to Collision makes it infeasible/impracticable/impossible to find values X and Y, where X ≠ Y, yet H(x) = H(y).
Resistance to Preimage
Resistance to Preimage is when it is computationally infeasible/impossible to find the input to any specified cryptographic hash output. With Resistance to Preimage, locating the input that matches a hash output is impossible.
2.- Use tronscan and etherscan to verify the hash of the last block and the hash of that transaction. Screenshot is required for checking.
Verifying Hash with Etherscan
To verify the hash of the latest block and the hash of the latest transaction using Etherscan, I visited https://etherscan.io/
I scroll to the latest block page and picked the latest block #12761454
To get the hash for the block, I clicked on the block and opened the page to all instructions such as the number of transactions in the block, the time the block was hashed, the parent hash and so on.
The hash to the block is [0x09e0175578595d7942a3b907e50a6f3c1adcab417fc834f79cd4f46920389a5b]. To view the hash, you can click on it here https://etherscan.io/block/0x09e0175578595d7942a3b907e50a6f3c1adcab417fc834f79cd4f46920389a5b
The block can either be viewed by its Block ID or through its hash. You input the hash or Block ID in the search column.
There are a total of 225 transactions in the block
Verifying Hash with Tronscan
To view the latest block through Tronscan, you click on https://tronscan.org, scroll to the block section and click on more
After clicking on more, I got to the block page and I pick the last block #31645342.
I clicked on the Block and got to the page where the entire details of the block is displayed including the number of transaction, block hash and so on.
The Block hash for the block is [0000000001e2de9e4abae54b07ae72cf5abcb8b4beaa2d3633b753abb48e71fc] and it can be viewed by clicking https://tronscan.org/#/block/31645342
3.- Generate the hash using SHA-256 , from the word CryptoAcademy and from cryptoacademy. Screenshot required. Do you see any difference between the two words? Explain.
In other to check for the Hash of the word CryptoAcademy and the word cryptoacademy, I clicked on https://passwordsgenerator.net/sha256-hash-generator/.
When I searched for the Hash of CryptoAcademy using SHA256, the result was D03CA34B258E6E0FD06B2070DDE61B50BD4EEF6161A8EDAA4A420C9AE1BEB7F9
When I searched for the Hash of cryptoacademy using SHA256, the result was 0592F5DD27DC72E675B2AB9C77487A69FAAF84196597FA052EC099C18EE7C4C5
The two words gave different Hashes, this is because the words have different cases, with one having Uppercase (Capital letter) and the other not having any Uppercase. This is simply to show that Hash is resistant to collision since two different word case can't give the same result.
4.- In your own words explain the difference between hash and cryptography.
HASH
Hash are cryptographic functions used to encode data into a specific alphanumeric string for security, privacy and anonymity. Hash are irreversible, and thet have a fixed lenght.
Cryptography
Cryptography is the encryption of a data so a third party without authorization cannot access it or read its meaning thereby preventing alteration by the third party. With cryptography, only authorized users who poccess the key can access the original data
| Function | Hash | Cryptography |
|---|---|---|
| KEY | Hash do not use keys | Cryptography uses keys to retrieve information |
| Retrievable | Data encoded in hashes cannot be retrieved | Cryptography encodings can be retrieved by the parties with the keys |
| Lenght of Encoding | Lenght is fixed | Lenght is not fixed, it grows with the increase in information. |
Conclusion
Cryptography and Hashing are important for encoding data for the sake security and anonymosity. It is no doubt that both cryptography and hashing has been very important in blockchain and cryptocurrency.
I must say that it was a great pleasure being a part of this class and thanks to @pelon53 for teaching such great lecture.
Gracias por participar en Steemit Crypto Academy Season 3:
Espero seguir leyendo tus publicaciones.
Con respecto a la resistencia a la colisión, existe la posibilidad de que ocurra, no es imposible, perro mientras más pequeña sea esa posibilidad que ocurra una colisión, entonces tiene mayor resistencia a la colisión. No hay ninguna función hash sin colisión, lo que ocurre es algunas son muy fuertes a la resistencia a la colisión, como SHA-256.
En cuanto a la resistencia a la preimagen, existe la posibilidad de que un atacante adivine cual es la entrada al observar una salida. Aunque sean muy bajas las posibilidades.
la 2da pregunta se refiere a encontrar el hash del bloque y de la transacción, y solo vi el hash del bloque, no el de la transacción.
Con respeto al blog, es importante justificar el texto y que las conclusiones sean más sustanciosas.
Sigue adelante, lo puedes hacer mejor.
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