I was recently reading that MD5 is "broken" because it's pretty easy to generate collisions (like
2^(L/2)). And the SHA1 (theoretically) fares no better. The solution seems to be hash algorithms that are very slow in comparison.
I am wondering why can't people combine these fast algorithms to get the best of both security and speed? What would be the time complexity to generate a simultaneous MD5 and SHA1 collision? And if it's hard enough, would these make a viable candidate for collision resistant hash applications?
(By simultaneous collision I mean generating a string with same MD5 and SHA1)