Potential problem with RIPEMD160 removal from newer OpenSSL versions by default

[kristapsk]

See bitcoin-core/HWI#305 and openssl/openssl#16994.

Bitcoin Core solved it by writing own pure Python RIPEMD160 implementation (see bitcoin/bitcoin#23716), but it's meant to be used only for tests as it isn't constant time.

[dgpv]

#65 should solve this (taken the code from Core's test framework)

I'm not sure if 'constant time' is relevant here. Hash160 function is not supposed to work with any secret data.

It will likely be much slower than openssl implementation that is used by python, but given that ripemd160 is already not available from python.hashlib in some linux distributions, we'll have to bear this this.

[dgpv]

(edit: moved this comment about Core's implementation described as "Test only" to the PR, it is more appropriate there: #65 (comment))