This question already has an answer here:
I know this is a real dumb question and I am certainly talking complete rubbish, but let me explain:
- We have a long SHA-256 hash, e.g.:
- Now we use the long hash to create one SHA-1 and one MD5 hash and combine them.
c49e2143913627ea178e66571189628a41526bf3(SHA-1; 160bit) +
So now we got this:
(SHA-1 + MD5; 160bit + 128bit = 288bit)
And it is longer than the input string, with 288bit instead of 256bit. So did we actually increased the entropy?
In short this is this:
hash = sha256(input) # 256bit result = sha1(hash) + md5(hash) # 288bit
(That is supposed to be pseudo-code, don't know if it is valid through.)
What is the error in reasoning here? I am sure you cannot increase entropy/string length in this way...
Edit: Also important: Did I possibly even decreased the entropy this or stayed it the same?