Function to enable safe SHA-1 hashing:
Collision attacks are thwarted by hashing a detected near-collision block 3 times.
Think of it as extending SHA-1 from 80-steps to 240-steps for such blocks:
- The best collision attacks against SHA-1 have complexity about 2^60,
- thus for 240-steps an immediate lower-bound for the best cryptanalytic attacks would be 2^180.
- An attacker would be better off using a generic birthday search of complexity 2^80.
+ The best collision attacks against SHA-1 have complexity about 2^60,
+ thus for 240-steps an immediate lower-bound for the best cryptanalytic attacks would be 2^180.
+ An attacker would be better off using a generic birthday search of complexity 2^80.
Enabling safe SHA-1 hashing will result in the correct SHA-1 hash for messages where no collision attack was detected,
but it will result in a different SHA-1 hash for messages where a collision attack was detected.