johnjjung / blockchain

A blockchain implementation

Blockchain

Having fun implementing a blockchain using Golang.

Using Minimum Viable Blockchain

Keys

The Blockchain uses ECDSA (224 bits) keys. When a user first joins the blockchain a random key will be generated.

Keys are encoded using base58.

Given x, y as the components of the public key, the key is generated as following:

	base58(BigInt(append(x as bytes, y as bytes)))

Proof of work

In order to sign a transaction and send it to the network, proof of work is required.

Proof of work is also required for block generation.

Protocol

The blockchain runs on port 9191 and uses TCP to handle connections among peers.

Message

• Message type (1 byte)

   const (
   	MESSAGE_GET_NODES = iota + 20
   	MESSAGE_SEND_NODES
  
   	MESSAGE_GET_TRANSACTION
   	MESSAGE_SEND_TRANSACTION
  
   	MESSAGE_GET_BLOCK
   	MESSAGE_SEND_BLOCK
   )
  

• Options (4 bytes): Data specific
• Data (n bytes): Data specific

Transaction

• Header:

  • From (80 bytes): Origin public key
  • To (80 bytes): Destination public key
  • Timestamp (4 bytes): int32 UNIX timestamp
  • Payload Hash (32 bytes): sha256(payloadData)
  • Payload Length (4 bytes): len(payloadData)
  • Nonce (4 bytes): Proof of work

• Signature (80 bytes): signed(sha256(header))

• Payload data (Payload Length bytes): raw data

Block

• Header:

  • Origin (80 bytes): Origin public key
  • Timestamp (4 bytes): int32 UNIX timestamp
  • Previous block (32 bytes): sha256(previous block header)
  • Merkel Root (32 Bytes): sha256(transaction hashes)
  • Nonce (4 bytes): int32 UNIX timestamp

• Signature (80 bytes): signed(sha256(header))

• Block transactions