Bitcoin's static proof-of-work function SHA256(SHA256(data)) was apparently easy enough to be implement as ASIC which lead to the re-centralization we see today.
But what if the PoW function changes for every new block based on the hash of the last block mined? One could generate a new hash chain by seeding a commonly known PRNG with the hash of the last block and use it to generate a chain of hash functions from a (large) pool of commonly known hash functions.
- RIPEMD(SHA2(SHA3(MD5(RIPEMD(SHA2(data)))))) => digest (i.e. old block header hash)
- PRNG(digest) => SHA2(MD5(SHA3(SHA3(RIPEMD(RIPEMD(data))))))
- digest (i.e. new block header hash)
This way every miner would know how to generate the new chain of hash functions which has to be used to generate a digest with certain criteria (leading zeros) for the next block but nobody could calculate the subsequently hash chains and nobody could implement static hash chain circuits but has to use FPGAs which have to be reprogrammed every block and have to be able to host every possible hash chain constellation. If the hash chains are complex enough it might even lead to a decrease in FPGA efficiency which would favour general computing hardware and reinstate the "one-CPU-one-vote" principle.
What do you think of this approach? Why might it be flawed?