An implementation of blockchain in Golang.
Initial (now redundant) approach was to store the Blocks containing SHA-256 Hashes of the current and previous blocks along with the data (usually the transactions).
Later revisions added a CLI support using Golang's builtin os.Args package.
The functionality to create custom transactions and store them as a ledger was introduced after 66b9b8d.
$ go get github.com/boltdb/bolt
$ go get github.com/eiannone/keyboard
▶ go build
Usage: blockchain [addblock] [printchain ...]Current restriction on calculating block hash is to have a certain length of 0s (18 as of now, see here) at the beginning. However, it is technically impossible to calculate reasonable amount of hashes in a minute (generally takes years). Keeping that in mind, I've set the limit to 4.
The hash function repeatedly calculates the hashes in order until it finds one which satisfies the restriction.
for nonce < maxNonce {
/* Retrieve the data for given PoW */
data := pow.prepareData(nonce)
/* Calculate it's SHA hash */
hash := sha256.Sum256(data)
fmt.Printf("\r%x", hash)
hashInt.SetBytes(hash[:])
/* If the calculated hash was less than target then we exit */
if hashInt.Cmp(pow.target) == -1 {
fmt.Printf("\n\n")
return nonce, hash[:]
} else {
nonce++
}
}The nonce is incremented after each iteration to inculcate the randomness in
hash generation.
The block structure is defined as follows.
type Block struct {
Timestamp int64 /* Time of block creation */
Data []byte /* Valuable info in the block */
PrevBlockHash []byte /* Hash of the previous block */
Hash []byte /* Hash of the block */
Nonce int /* Random nonce for PoW */
}POW is important in a sense that it enables us to validate whether the existing transactions are frivolous or are they actually correct. The Proof of Work algorithm validates whether the individual instances of every block satisfies the length restriction and that the sha256 of its data and timestamp is matches the pre-computed value.
- Extract unspent coins
- Network interaction
- Bitcoin client nodes
- Private wallets
Thanks to the wonderful Golang documentation obviously! Apart from it, ideas were picked up from these sources.
Set targetBits in utils.go as something above 20 (say 25) and watch your CPU blow up 😛