Can sha1sum return the same results for two files that are different ?
I am asking this both from a theoretical and practical point of view.
Can sha1sum return the same results for two files that are different ? I
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Can sha1sum return the same results for two files that are different ?
I am asking this both from a theoretical and practical point of view.
Mathematically, all hash functions have collisions — that is, two inputs can return the same hash. This is true for any function that has an input of
Nbits and an output ofMbits, whereM<N.A cryptographically sound hash algorithm, however, produces a hash that is so unpredictable, it would take millions of years to guess your way to an input that produces a particular hash. Some hash algorithms have known weaknesses that make this easier; when this happens the hash is considered ‘broken’ and everybody is supposed to switch to a new, better algorithm.
Though I don’t follow crypto news that closely, SHA-1 is considered broken, so in theory if you can find the right tools, you can generate two files with the same SHA1 output.