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Break my stupid hash function

by quackduck on 8/7/22, 1:58 AM with 3 comments

I made this crappy, most likely very insecure hash function with zero actual cryptographic hash knowledge while on a plane.

If you can find a collision or find the preimage of f11e7def9c2ec4c0, you'll officially have broken it.

Link: https://gist.github.com/quackduck/0da5d2ed7807e3ef22dc2e0cdadbf90a

by gus_massa on 8/7/22, 3:55 AM
With
```
    300000002a00000041e00000
```
I get
```
    e078387cb36ec4c0
```
your hash is
```
    f11e7def9c2ec4c0
```
so I reversed 5 chars.
In line 39 it says "num*num" where num is the value of each 8 character block, so if I make each block a multiple of a power of 16, it will not modify the last character of the output. So I can discover each character one by one. I should be padding with \null instead of 0, but it somewhat works anyway.
Also, you use 0x428a2f98 as a magic constant, but you should use an odd numbers instead of an even one. If not, you lose the last bits. If you take a look at the output of your hash, the last character is always 0 or 8.
by developedbytoby on 8/7/22, 2:07 AM
incredible.