What is blockchain? As a Ruby developer, the best way to understand blockchain
is to implement one yourself. With just 50 lines of Ruby code you can thoroughly understand the core principles of blockchain technology!
If you want to start learning Ethereum blockchain application development right away, you can visit Huizhi.com's excellent online interactive tutorial:
Blockchain = a linked list of blocks?
class Block
attr_reader :timestamp
attr_reader :data
attr_reader :previous_hash
attr_reader :hash
def initialize(data, previous_hash)
@timestamp = Time.now
@data = data
@previous_hash = previous_hash
@hash = calc_hash
end
def self.first( data="Genesis" ) # create genesis (big bang! first) block
## note: uses all zero for previous_hash ("0")
Block.new( data, "0000000000000000000000000000000000000000000000000000000000000000" )
end
def self.next( previous, data="Transaction Data..." )
Block.new( data, previous.hash )
end
private
def calc_hash
sha = Digest::SHA256.new
sha.update( @timestamp.to_s + @previous_hash + @data )
sha.hexdigest
end
end # class Block
#####
## let's get started
## build a blockchain a block at a time
b0 = Block.first( "Genesis" )
b1 = Block.next( b0, "Transaction Data..." )
b2 = Block.next( b1, "Transaction Data......" )
b3 = Block.next( b2, "More Transaction Data..." )
blockchain = [b0, b1, b2, b3]
pp blockchain
Execute the above program:
~$ ruby blockchain.rb
will output something like the following:
[#<Block:0x1eed2a0
@timestamp = 1637-09-15 20:52:38,
@data = "Genesis",
@previous_hash = "0000000000000000000000000000000000000000000000000000000000000000",
@hash = "edbd4e11e69bc399a9ccd8faaea44fb27410fe8e3023bb9462450a0a9c4caa1b">,
#<Block:0x1eec9a0
@timestamp = 1637-09-15 21:02:38,
@data = "Transaction Data...",
@previous_hash = "edbd4e11e69bc399a9ccd8faaea44fb27410fe8e3023bb9462450a0a9c4caa1b",
@hash = "eb8ecbf6d5870763ae246e37539d82e37052cb32f88bb8c59971f9978e437743">,
#<Block:0x1eec838
@timestamp = 1637-09-15 21:12:38,
@data = "Transaction Data......",
@previous_hash = "eb8ecbf6d5870763ae246e37539d82e37052cb32f88bb8c59971f9978e437743",
@hash = "be50017ee4bbcb33844b3dc2b7c4e476d46569b5df5762d14ceba9355f0a85f4">,
#<Block:0x1eec6d0
@timestamp = 1637-09-15 21:22:38,
@data = "More Transaction Data...",
@previous_hash = "be50017ee4bbcb33844b3dc2b7c4e476d46569b5df5762d14ceba9355f0a85f4",
@hash = "5ee2981606328abfe0c3b1171440f0df746c1e1f8b3b56c351727f7da7ae5d8d">]
Wait a minute, is blockchain a linked list?
of course not. Our purpose in using a linked list is to get a reference to the previous block: in a blockchain, each block must have an identifier,
and this identifier must also depend on the previous block's identifier, which means that if you To replace a block in the blockchain, the identifiers of all
subsequent . In the above implementation, you can see that when we call calc_hash
the method to calculate the block's identifier, we need to
pass in the signature of the previous block, which is what it means.
What about proof-of-work algorithms?
Now let's add the implementation of the proof-of-work algorithm. In the classic blockchain, you have to calculate the hash starting with 00 as
the identifier. The more 0s prefixed, the greater the amount of calculation and the more difficult it is. For simplicity, let's set the difficulty to be two prefixed 0s,
that is, 2^16 = 256 possibilities.
blockchain_with_proof_of_work.rb:
def compute_hash_with_proof_of_work( difficulty="00" )
nonce = 0
loop do
hash = calc_hash_with_nonce( nonce )
if hash.start_with?( difficulty )
return [nonce,hash] ## bingo! proof of work if hash starts with leading zeros (00)
else
nonce += 1 ## keep trying (and trying and trying)
end
end
end
def calc_hash_with_nonce( nonce=0 )
sha = Digest::SHA256.new
sha.update( nonce.to_s + @timestamp.to_s + @previous_hash + @data )
sha.hexdigest
end
Now we run this blockchain program with POW mechanism added:
~$ ruby blockchain_with_proof_of_work.rb
The output is as follows:
[#<Block:0x1e204f0
@timestamp = 1637-09-20 20:13:38,
@data = "Genesis",
@previous_hash = "0000000000000000000000000000000000000000000000000000000000000000",
@nonce = 242,
@hash = "00b8e77e27378f9aa0afbcea3a2882bb62f6663771dee053364beb1887e18bcf">,
#<Block:0x1e56e20
@timestamp = 1637-09-20 20:23:38,
@data = "Transaction Data...",
@previous_hash = "00b8e77e27378f9aa0afbcea3a2882bb62f6663771dee053364beb1887e18bcf",
@nonce = 46,
@hash = "00aae8d2e9387e13c71b33f8cd205d336ac250d2828011f5970062912985a9af">,
#<Block:0x1e2bd58
@timestamp = 1637-09-20 20:33:38,
@data = "Transaction Data......",
@previous_hash = "00aae8d2e9387e13c71b33f8cd205d336ac250d2828011f5970062912985a9af",
@nonce = 350,
@hash = "00ea45e0f4683c3bec4364f349ee2b6816be0c9fd95cfd5ffcc6ed572c62f190">,
#<Block:0x1fa8338
@timestamp = 1637-09-20 20:43:38,
@data = "More Transaction Data...",
@previous_hash = "00ea45e0f4683c3bec4364f349ee2b6816be0c9fd95cfd5ffcc6ed572c62f190",
@nonce = 59,
@hash = "00436f0fca677652963e904ce4c624606a255946b921132d5b1f70f7d86c4ab8">]
Do you see the difference from the previous version? Now everything hash
starts with 00, nonce
which is
the hash.
Original: 50 lines of ruby code let you thoroughly understand what a blockchain is