问题
Is there an x where SHA1(x) == x?
I'm looking for a proof or a strong argument against it.
回答1:
The same arguments apply here as for the question Is there an MD5 fixed point? I.e. for a randomly chosen function it is about 63%.
回答2:
Read about fixed point attack on this wiki entry One-way compression function - Davies-Meyer
Most widely used hash functions, including MD5, SHA-1 and SHA-2
use Merkle-Damgård construction.
来源：https://stackoverflow.com/questions/2340524/is-there-any-x-for-which-sha1x-equals-x