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Consider a hash function that starts with an 32-bit initial value of c09db506 and repeatedly XORs it with 32-bit blocks of the input to produce a 32-bit output. For example, the input de0fc223 would generate the following output:

(de0fc223) = c09db506 ⊕ de0fc223 = 1e927725and the input cd1aa915 f08d7db7 would generate the following output:
(cd1aa915 f08d7db7) = c09db506 ⊕ cd1aa915 ⊕ f08d7db7 = fd0a61a4
1- Approximately how many steps would be required to perform a brute force attack to find a preimage for a given output of this hash function?
2- Approximately how many steps would be required to perform a brute force birthday attack to find a collision for this hash function?
3- Use the properties of the XOR operation to find a 32-bit preimage for the output 666cdce9
4- Find a 32-bit second preimage for the output fd0a61a4 calculated above.
5- Find a collision other than the one demonstrated by your answer to (4). (hint: pick a 32-bit input, then find a 64-bit input that generates the same output using the properties of XOR.)

User Vindia
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Final answer:

To perform a brute force attack, it would take approximately 4,294,967,296 steps. To perform a birthday attack, it would take approximately 77,165 steps. Using the properties of XOR, a 32-bit preimage and a second preimage can be found.

Step-by-step explanation:

To perform a brute force attack to find a preimage for a given output of this hash function, you would need to try all possible inputs until you find one that produces the desired output. Since the hash function produces a 32-bit output, there are a total of 2^32 possible inputs. Therefore, it would take approximately 4,294,967,296 steps to perform a brute force attack.

To perform a brute force birthday attack to find a collision for this hash function, you would need to find two inputs that produce the same output. The birthday paradox states that the probability of finding a collision in a hash function with a 32-bit output is approximately 50% after trying approximately 77,165 inputs. Therefore, it would take approximately 77,165 steps to perform a brute force birthday attack.

To find a 32-bit preimage for the output 666cdce9, we can use the properties of XOR. The XOR operation is reversible, meaning that if we XOR the output with the original input, we will get the initial value of c09db506. So, by XORing 666cdce9 with c09db506, we can find the 32-bit preimage.

To find a 32-bit second preimage for the output fd0a61a4, we can use the same approach as in question 3. By XORing fd0a61a4 with c09db506, we can find another 32-bit input that produces the same output.

To find a collision other than the one demonstrated in question 4, we can pick a random 32-bit input and find a 64-bit input that produces the same output using the properties of XOR. By XORing the 64-bit input with c09db506, we can find a 32-bit input that generates the same output.

User Menawer
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