Question Suggestion : Use sha1 Instead of md5

[semprot]

Hello.

I suggest you to use sha1 instead of md5 to generate unique id for cache name,
because sha1 result is longer than md5 result (40 vs 32 characters).
8 more characters = more permutations available = less collision chance.
Think about site with tons of pages.
More cache name permutations.

Thank you

 

[Fillip H.]

So, an MD5 hash is a 32 character string where each character is a hexadecimal number (0-9 + A-F), meaning you have 16³² possible combinations. 16³² = 3.402823669 x 10³⁸, or roughly 3 with 38 zeroes afterwards.

340,282,366,900,000,000,000,000,000,000,000,000,000 is a very large number, I sure don't know how to pronounce that number

With the new change to the Filecache system that separates each cache prefix into its own subfolder, that means that each individual feature, such as Data Registry, can support up to that many data registry entries before collisions occur.

But let's take it a step further. Let's say on average, each of those files is 1 KB in size. We now have the following number: 3.484491437 x 10⁴¹ - this number is the amount of bytes needed to store all this information on your server. The largest unit of storage known to man at the moment, according to Wikipedia, is a Yottabyte, or 1.20892582 x 10²⁴.

A yottabyte, from my understanding, is a terabyte terabytes. If that understanding is correct, you would need a yottabyte yottabytes of HD space in order to store enough information to support all the possible combinations an MD5 hash can generate for a 1 KB file.

In short, I'm going to say that the speed of MD5 makes it a more suitable hashing algorithm for this purpose


(This post was done a bit tongue-in-cheek since hash collisions can occur, but since this is not being used as a cryptographic measure where the user can manipulate the hash to try to bypass a cryptographic system, the chances of hash collision is very, very low)

 

[semprot]

I think you are correct. I think before collision happens, my disk will be full first / my RAM usage will be 100% first

 

[DragonByte Technologies]

Hello semprot,

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