Use pysha3 on python<3.9

[xloem]

Looks like safe-pysha3 is only compatible with python3.9 and above, so I added specifiers to select the dependency depending on python version.

[ctrl-Felix]

Thank you for suggesting this change.

To me it seems like the pysha3 package is only supported for python 2.7 - python 3.5 which would still mean it won't work on 3.6, 3.7 and 3.8.

The whole issue about this is that Ethereum uses KECCAK256 as hashing algorithm (https://ethereum.stackexchange.com/a/554) which has been replaced by SHA3 in 2015. And therefore it is actually quite hard to maintain.

I am not sure how web3py handles keccak. But I remember that it was one of the hardest challenges I faced when adding Evmos and EVM support.

What are your thoughts on this. Maybe pysha3 works also for python3.5+, do you know that?

[xloem]

• Both libraries appear to support the original keccak algorithm
• pysha3’s last release was in February of 2017, which is before python 3.6 was released. This is why it only mentions python 3.5 .
• safe-pysha3 made two changes to pysha3, which are listed at tiran/pysha3@master...5afe:pysha3:master :
  1. it forward-ported the code to python 3.11 by changing a type symbol, i briefly found this mentioned at Request for PEP 387 exception: Py_SET_TYPE python/steering-council#79 . this broke compatibility with python 3.8 and below.
  2. it addressed a security vulnerability with processing data larger than 2^32 - 200 bytes.

So, assuming all data is not that big, the change looks okay now, but if there are further security fixes they will not be integrated which is unfortunate.

[ctrl-Felix]

Alright. Thanks for providing further clarification. I will merge it then.