Blockchain R

block_example = list(index = 1,
                      timestamp = "2018-01-05 18.00 GMT",
                      data = "some data",
                      previous_hash = 0,
                      proof = 9,
                      new_hash = NULL)

#################################################################

library("digest")
digest("Manish" ,"sha256")
digest("BD" ,"sha256")
###############################################################

#Function that creates a hashed "block"
hash_block = function(block){
  block$new_hash <- digest(c(block$index,
                             block$timestamp,
                             block$data,
                             block$previous_hash), "sha256")
  return(block)
}
#################################################################

### Simple Proof of Work Alogrithm
proof_of_work <- function(last_proof){
  proof <- last_proof + 1
 
  # Increment the proof number until a number is found that is divisable by 99 and by the proof of the previous block
  while (!(proof %% 99 == 0 & proof %% last_proof == 0 )){
    proof <- proof + 1
  }
  return(proof)
}
##################################################################

#A function that takes the previous block and normally some data (in our case the data is a string indicating which block in the chain it is)
gen_new_block <- function(previous_block){
 
  #Proof-of-Work
  new_proof <- proof_of_work(previous_block$proof)
 
  #Create new Block
  new_block <- list(index = previous_block$index + 1,
                    timestamp = Sys.time(),
                    data = paste0("this is block ", previous_block$index +1),
                    previous_hash = previous_block$new_hash,
                    proof = new_proof)
 
  #Hash the new Block
  new_block_hashed <- hash_block(new_block)
 
  return(new_block_hashed)
}
############################################################################

# Define Genesis Block (index 1 and arbitrary previous hash)
block_genesis <-  list(index = 1,
                       timestamp = Sys.time(),
                       data = "Genesis Block",
                       previous_hash = "0",
                       proof = 1)
########################################################################

blockchain <- list(block_genesis)
previous_block <- blockchain[[1]]

# How many blocks should we add to the chain after the genesis block
num_of_blocks_to_add <- 5

# Add blocks to the chain
for (i in 1: num_of_blocks_to_add){
  block_to_add <- gen_new_block(previous_block)
  blockchain[i+1] <- list(block_to_add)
  previous_block <- block_to_add
 
  print(cat(paste0("Block ", block_to_add$index, " has been added", "\n",
                   "\t", "Proof: ", block_to_add$proof, "\n",
                   "\t", "Hash: ", block_to_add$new_hash)))
}