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I'm curious, how can for example SHA-256 be unique if there are only a limited number of them?!

For clarification:
how many MD5 hashes are there?
$16^{32}$ MD5 hashes can be produced. $16^{64}$ SHA-256 hashes can be produced.
while there are $16^{128}$ just SHA-512 hashes, let alone long texts.

For more clarification:
assume we want MD5 of all the SHA-256 hashes.
we can have $16^{32}$ number of MD5 hashes, while there are $16^{64}$ SHA-256 hashes.
we will have 3.4*$10^{38}$ duplicate MD5 hashes!

And so is for SHA-256 hash, if we calculate SHA-256 of all the SHA-512 hashes, we will have 1.15*$10^{77}$ duplicate SHA-256 hashes!

I'm curious, how can for example SHA-256 be unique if there are only a limited number of them?!

For clarification:
how many MD5 hashes are there?
$16^{32}$ MD5 hashes can be produced. $16^{64}$ SHA-256 hashes can be produced.
while there are $16^{128}$ just SHA-512 hashes, let alone long texts.

For more clarification:
assume we want MD5 of all the SHA-256 hashes.
we can have $16^{32}$ number of MD5 hashes, while there are $16^{64}$ SHA-256 hashes.
we will have 3.4*$10^{38}$ duplicate MD5 hashes!

And so is for SHA-256 hash, if we calculate SHA-256 of all the SHA-512 hashes, we will have 1.15*$10^{77}$ duplicate SHA-256 hashes!

Edit: This is not limited to a particular hash like SHA-256.

I'm curious, how can for example SHA-256 be unique if there are only a limited number of them?!

for clarifying: how many MD5 hashes are there? $16^{32}$ MD5 hashes can be produced. $16^{64}$ SHA-256 hashes can be produced. while there are $16^{128}$ just SHA-512 hashes, let alone long texts.

for more clarifying: assume we want MD5 of all the SHA-256 hashes. we can have $16^{32}$ number of MD5 hashes, while there are $16^{64}$ SHA-256 hashes. we will have 3.4*$10^{38}$ duplicate MD5 hashes!

And so is for SHA-256 hash, if we calculate SHA-256 of all the SHA-512 hashes, we will have 1.15*$10^{77}$ duplicate SHA-256 hashes!

I'm curious, how can for example SHA-256 be unique if there are only a limited number of them?!

For clarification: 
how many MD5 hashes are there? 
$16^{32}$ MD5 hashes can be produced. $16^{64}$ SHA-256 hashes can be produced. 
while there are $16^{128}$ just SHA-512 hashes, let alone long texts.

For more clarification: 
assume we want MD5 of all the SHA-256 hashes. 
we can have $16^{32}$ number of MD5 hashes, while there are $16^{64}$ SHA-256 hashes. 
we will have 3.4*$10^{38}$ duplicate MD5 hashes!

And so is for SHA-256 hash, if we calculate SHA-256 of all the SHA-512 hashes, we will have 1.15*$10^{77}$ duplicate SHA-256 hashes!

I'm curious, how can for example SHA-256 be unique if there is only a limited number of them?!

for clarifying: how many MD5 hashes are there? 16^32 MD5 hashes can be produced. 16^64 SHA-256 hashes can be produced. while there are just 16^128 SHA-512 hashes, let alone long texts?

for more clarifying: assume we want MD5 of all the SHA-256 hashes. we can have 16^32 number of MD5 hashes, while there are 16^64 SHA-256 hashes. we will have 3.4*10^38 duplicate MD5 hashes!

And so is for SHA-256 hash, if we calculate SHA-256 of all the SHA-512 hashes, we will have 1.15*10^77 duplicate SHA-256 hashes!

I'm curious, how can for example SHA-256 be unique if there are only a limited number of them?!

for clarifying: how many MD5 hashes are there? $16^{32}$ MD5 hashes can be produced. $16^{64}$ SHA-256 hashes can be produced. while there are $16^{128}$ just SHA-512 hashes, let alone long texts.

for more clarifying: assume we want MD5 of all the SHA-256 hashes. we can have $16^{32}$ number of MD5 hashes, while there are $16^{64}$ SHA-256 hashes. we will have 3.4*$10^{38}$ duplicate MD5 hashes!

And so is for SHA-256 hash, if we calculate SHA-256 of all the SHA-512 hashes, we will have 1.15*$10^{77}$ duplicate SHA-256 hashes!