Being a radical change to Bitcoin transaction perfrmance, MimbleWimble was a very powerful way anonymously introduced in July 2016.
MimbleWimble is a name of a tongue-tying curse from the Harry Potter series. Its goal is removing transactions totally from blocks. The transactions consist of input amounts, output amounts, and a signature only. The verification of the transaction is to be made by the receiver only.
In fact, a block consists of the list of all the transaction input amounts, output amounts, and corresponding signatures only. Blocks are pairs of input and output amounts, so they can be merged with previous blocks. Nodes are able to ensure that extra bitcoins are not created by blocks transactions without any necessity of decrypting transactions.
The transaction storage removal guarantees total anonymity to each user when denying the ability of generating the transaction history. Moreover, the blockchain size can be decreased by more than 60% with blocks which contain only the unspent transaction outputs, i.e. the Bitcoins which have been received, and not moved out yet. Nodes will need to watch only the unspent transaction outputs, and that increases performance a lot.
MimbleWimble of course renders great advantages and technical progress, but the implementation demands removing the system of Bitoin’s Script. Thus, the implementation of MimbleWimble isn’t possible technically.
Sidechain(a separate blockchain attached directly to the blockchain of Bitcoin with the help of a two-way peg usage)is one of the proposals to make MimbleWimble exist. Users could exchange Bitcoins for MimbleWimble coins, complete totally rapid and private transactions on the chain of MimbleWimble, and then exchange these coins for Bitcoin anytime they wish.
The group of developers is currently developing MimbleWimbleas GRIN (a separate cryptocurrency), it might be launched on the nearest future.