The ultimate alt-coin would be a solid implementation of MimbleWimble.
Even better if it has a memory-bound instantly-verifiable proof-of-work...
Is there a source for MimbleWimble yet?
No; there is no implementation of MimbleWimble yet.
Just an outline of the basic cryptographic ideas at
http://diyhpl.us/~bryan/papers2/bitcoin/mimblewimble.txtA number of Bitcoin Core developers have expressed keen interest though, as can be
seen in this interview transcript:
http://diyhpl.us/wiki/transcripts/mimblewimble-podcast/It holds great promise in hugely advancing both anonymity and scalability.
and can you explain what memory-bound instantly-verifiable proof-of-work is and if it has been used in a coin?
A proof of work that, like bitcoin's, can be instantly verified with no memory use
(a very desirable property that's lost in Litecoin, Monero, Ethereum, and many others)
but for which mining requires hundreds of megabytes of memory.
The first attempt at such a PoW was Momentum, but it turns out to be broken, allowing
memory to be traded off against computation.
The other two are Cuckoo Cycle and Equihash, the latter of which will be used in the upcoming
Zcash. Cuckoo Cycle is unique in that mining reduces to reading and writing individual random
bits, as explained in
http://cryptorials.io/beyond-hashcash-proof-work-theres-mining-hashingand as such can be indirectly useful in supporting the development of more energy efficient DRAM
technology.