Swift-Blockchain-Proof

Proof.swift

    /**
     Simple Proof of Work Algorithm:
     
     - Find a number p' such that hash(pp') contains leading 4 zeroes, where p is the previous p'
     - p is the previous proof, and p' is the new proof
     - Parameter: last_proof: Int64
     - returns: Int64
     */
    func proofOfWork(last_proof: Int64) -> Int64 {
        var proof: Int64 = 0
        while !self.validProof(last_proof: last_proof, proof: proof) {
            proof += 1
        }
        
        return proof
    }
    
    /**
     Validates the Proof: Does hash(last_proof, proof) contain 4 leading zeroes?
     
     - Parameter last_proof: <int> Previous Proof
     - Parameter proof: <int> Current Proof
     - returns: True if correct, False if not.
     */
    func validProof(last_proof: Int64, proof: Int64) -> Bool {
        let guess = "\(last_proof)\(proof)"
        let guess_hash = guess.sha256()
        return guess_hash.suffix(4) == "0000"
    }