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I want to perform a collision attack using hash function of my student number and another possible student number with same hash value. How can I perform this? is there any online tools that can help me to find same hash value

For example

My student number is s3412347; Sha-1: 6b9e8b6fd49df67a7a770c28072e8b807cd2070e Possible student: sXXXXXXXX; Sha-1: 6b9e8b6fd49df67a7a770c28072e8b807cd2070e

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  • $\begingroup$ Study, it will take too long to impersonate another student successfully $\endgroup$ – kodlu Apr 24 at 3:38
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I want to perform a collision attack

Actually, the problem you cited is not a collision attack, but a second preimage attack.

In a collision attack, the attacker gets to select both messages; as long as they are distinct and hash to the same value, the attacker wins.

In a second preimage attack, the attacker is given one message, and is asked to find another message that hashes to the same value; if he can, he wins.

You have already specified one of the messages "s3412347"; the only flexibility the attacker is allowed is in the second message. Hence, this falls under "second preimage attack".

Here's why the distinction is important: for SHA-1, there are knowns ways to do collision attacks (which require rather more computational effort than what a student is likely able to get his hands on, and certainly not something you can find online for free); however there are no known feasible ways to do second preimage attacks.

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    $\begingroup$ And we'd need student numbers to be valid up to about 48 decimal digits to make it reasonably probable that a second preimage of the form sXX…XX exists, under reasonable assumptions about SHA-1. $\endgroup$ – fgrieu Apr 23 at 12:52
  • $\begingroup$ I tried XORing still no help. I know this question takes lots of trial and error $\endgroup$ – Denver1212 Apr 23 at 12:58
  • $\begingroup$ If the length is limited to 8 digits, a student probably has enough computational power and storage to brute force it. $\endgroup$ – Aman Grewal Apr 23 at 13:00
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    $\begingroup$ @AmanGrewal ... and notice that there are no such collisions... $\endgroup$ – SEJPM Apr 23 at 13:07

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