SegWit proposes significant backward compatibility. It hides its increased block size by changing the definition of a block to be measured as one million "units" instead of bytes. The "witness" signature data would be separated from the Merkle tree record of who is sending or receiving the bitcoin. The "witness" data is moved to the end, and each byte of it would only count as one quarter of a "unit". The overall effect would be changing the average block size to about 1.8 MB instead of 1.
To prove that a specific transaction is included in a block, a node only needs to produce log2(N) 32-byte hashes, constituting an authentication path or merkle path connecting the specific transaction to the root of the tree. This is especially important as the number of transactions increases, because the base-2 logarithm of the number of transactions increases much more slowly. This allows bitcoin nodes to efficiently produce paths of 10 or 12 hashes (320–384 bytes), which can provide proof of a single transaction out of more than a thousand transactions in a megabyte-size block.
Taking advantage of the cheap and plentiful hydroelectric power that an army of computers require, bitcoin mining is spreading in remote parts of China’s Sichuan province. In dark and isolated warehouses, bitcoin mining machines hum along solving equations to produce the highly valued cryptocurrency.
A company co-owned by one of President Vladimir Putin’s internet advisers plans to raise the cryptocurrency equivalent of as much as $100 million in a push to help Russian entrepreneurs challenge China in bitcoin mining.