254 lines
10 KiB
Go
254 lines
10 KiB
Go
// Copyright 2017-2021 DERO Project. All rights reserved.
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// Use of this source code in any form is governed by RESEARCH license.
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// license can be found in the LICENSE file.
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// GPG: 0F39 E425 8C65 3947 702A 8234 08B2 0360 A03A 9DE8
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//
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
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// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
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// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
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// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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package blockchain
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import "fmt"
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import "math/big"
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import "github.com/deroproject/derohe/block"
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import "github.com/deroproject/derohe/config"
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import "github.com/deroproject/derohe/cryptography/crypto"
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import "github.com/deroproject/derohe/globals"
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var (
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// bigZero is 0 represented as a big.Int. It is defined here to avoid
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// the overhead of creating it multiple times.
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bigZero = big.NewInt(0)
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// bigOne is 1 represented as a big.Int. It is defined here to avoid
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// the overhead of creating it multiple times.
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bigOne = big.NewInt(1)
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// oneLsh256 is 1 shifted left 256 bits. It is defined here to avoid
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// the overhead of creating it multiple times.
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oneLsh256 = new(big.Int).Lsh(bigOne, 256)
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// enabling this will simulation mode with hard coded difficulty set to 1
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// the variable is knowingly not exported, so no one can tinker with it
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//simulation = false // simulation mode is disabled
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)
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// HashToBig converts a PoW has into a big.Int that can be used to
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// perform math comparisons.
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func HashToBig(buf crypto.Hash) *big.Int {
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// A Hash is in little-endian, but the big package wants the bytes in
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// big-endian, so reverse them.
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blen := len(buf) // its hardcoded 32 bytes, so why do len but lets do it
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for i := 0; i < blen/2; i++ {
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buf[i], buf[blen-1-i] = buf[blen-1-i], buf[i]
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}
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return new(big.Int).SetBytes(buf[:])
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}
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// this function calculates the difficulty in big num form
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func ConvertDifficultyToBig(difficultyi uint64) *big.Int {
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if difficultyi == 0 {
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panic("difficulty can never be zero")
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}
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// (1 << 256) / (difficultyNum )
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difficulty := new(big.Int).SetUint64(difficultyi)
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denominator := new(big.Int).Add(difficulty, bigZero) // above 2 lines can be merged
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return new(big.Int).Div(oneLsh256, denominator)
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}
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func ConvertIntegerDifficultyToBig(difficultyi *big.Int) *big.Int {
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if difficultyi.Cmp(bigZero) == 0 {
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panic("difficulty can never be zero")
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}
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return new(big.Int).Div(oneLsh256, difficultyi)
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}
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// this function check whether the pow hash meets difficulty criteria
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func CheckPowHash(pow_hash crypto.Hash, difficulty uint64) bool {
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big_difficulty := ConvertDifficultyToBig(difficulty)
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big_pow_hash := HashToBig(pow_hash)
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if big_pow_hash.Cmp(big_difficulty) <= 0 { // if work_pow is less than difficulty
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return true
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}
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return false
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}
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// this function check whether the pow hash meets difficulty criteria
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// however, it take diff in bigint format
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func CheckPowHashBig(pow_hash crypto.Hash, big_difficulty_integer *big.Int) bool {
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big_pow_hash := HashToBig(pow_hash)
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big_difficulty := ConvertIntegerDifficultyToBig(big_difficulty_integer)
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if big_pow_hash.Cmp(big_difficulty) <= 0 { // if work_pow is less than difficulty
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return true
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}
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return false
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}
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// when creating a new block, current_time in utc + chain_block_time must be added
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// while verifying the block, expected time stamp should be replaced from what is in blocks header
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// in DERO atlantis difficulty is based on previous tips
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// get difficulty at specific tips,
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// algorithm is as follows choose biggest difficulty tip (// division is integer and not floating point)
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// diff = (parent_diff + (parent_diff / 100 * max(1 - (parent_timestamp - parent_parent_timestamp) // (chain_block_time*2//3), -1))
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// this should be more thoroughly evaluated
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// NOTE: we need to evaluate if the mining adversary gains something, if the they set the time diff to 1
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// we need to do more simulations and evaluations
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// difficulty is now processed at sec level, mean how many hashes are require per sec to reach block time
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func (chain *Blockchain) Get_Difficulty_At_Tips(tips []crypto.Hash) *big.Int {
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tips_string := ""
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for _, tip := range tips {
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tips_string += fmt.Sprintf("%s", tip.String())
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}
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if diff_bytes, found := chain.cache_Get_Difficulty_At_Tips.Get(tips_string); found {
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return new(big.Int).SetBytes([]byte(diff_bytes.(string)))
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}
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var MinimumDifficulty *big.Int
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change := new(big.Int)
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step := new(big.Int)
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if globals.IsMainnet() {
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MinimumDifficulty = new(big.Int).SetUint64(config.Settings.MAINNET_MINIMUM_DIFFICULTY) // this must be controllable parameter
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} else {
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MinimumDifficulty = new(big.Int).SetUint64(config.Settings.TESTNET_MINIMUM_DIFFICULTY) // this must be controllable parameter
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}
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GenesisDifficulty := new(big.Int).SetUint64(1)
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if len(tips) == 0 || chain.simulator == true {
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return GenesisDifficulty
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}
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height := chain.Calculate_Height_At_Tips(tips)
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// hard fork version 1 has difficulty set to 1
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/*if 1 == chain.Get_Current_Version_at_Height(height) {
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return new(big.Int).SetUint64(1)
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}*/
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/*
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// if we are hardforking from 1 to 2
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// we can start from high difficulty to find the right point
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if height >= 1 && chain.Get_Current_Version_at_Height(height-1) == 1 && chain.Get_Current_Version_at_Height(height) == 2 {
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if globals.IsMainnet() {
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bootstrap_difficulty := new(big.Int).SetUint64(config.MAINNET_BOOTSTRAP_DIFFICULTY) // return bootstrap mainnet difficulty
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rlog.Infof("Returning bootstrap difficulty %s at height %d", bootstrap_difficulty.String(), height)
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return bootstrap_difficulty
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} else {
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bootstrap_difficulty := new(big.Int).SetUint64(config.TESTNET_BOOTSTRAP_DIFFICULTY)
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rlog.Infof("Returning bootstrap difficulty %s at height %d", bootstrap_difficulty.String(), height)
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return bootstrap_difficulty // return bootstrap difficulty for testnet
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}
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}
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// if we are hardforking from 3 to 4
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// we can start from high difficulty to find the right point
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if height >= 1 && chain.Get_Current_Version_at_Height(height-1) <= 3 && chain.Get_Current_Version_at_Height(height) == 4 {
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if globals.IsMainnet() {
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bootstrap_difficulty := new(big.Int).SetUint64(config.MAINNET_BOOTSTRAP_DIFFICULTY_hf4) // return bootstrap mainnet difficulty
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rlog.Infof("Returning bootstrap difficulty %s at height %d", bootstrap_difficulty.String(), height)
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return bootstrap_difficulty
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} else {
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bootstrap_difficulty := new(big.Int).SetUint64(config.TESTNET_BOOTSTRAP_DIFFICULTY)
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rlog.Infof("Returning bootstrap difficulty %s at height %d", bootstrap_difficulty.String(), height)
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return bootstrap_difficulty // return bootstrap difficulty for testnet
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}
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}
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*/
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// until we have atleast 2 blocks, we cannot run the algo
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if height < 3 && chain.Get_Current_Version_at_Height(height) <= 1 {
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return MinimumDifficulty
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}
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// take the time from the most heavy block
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biggest_difficulty := chain.Load_Block_Difficulty(tips[0])
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parent_highest_time := chain.Load_Block_Timestamp(tips[0])
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// find parents parents tip from the most heavy block's parent
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parent_past := chain.Get_Block_Past(tips[0])
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past_biggest_tip := parent_past[0]
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parent_parent_highest_time := chain.Load_Block_Timestamp(past_biggest_tip)
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if biggest_difficulty.Cmp(MinimumDifficulty) < 0 {
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biggest_difficulty.Set(MinimumDifficulty)
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}
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block_time := config.BLOCK_TIME_MILLISECS
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step.Div(biggest_difficulty, new(big.Int).SetUint64(100))
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// create 3 ranges, used for physical verification
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switch {
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case (parent_highest_time - parent_parent_highest_time) <= block_time-1000: // increase diff
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change.Add(change, step) // block was found earlier, increase diff
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case (parent_highest_time - parent_parent_highest_time) >= block_time+1000: // decrease diff
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change.Sub(change, step) // block was found late, decrease diff
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change.Sub(change, step)
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default: // if less than 1 sec deviation,use previous diff, ie change is zero
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}
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biggest_difficulty.Add(biggest_difficulty, change)
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if biggest_difficulty.Cmp(MinimumDifficulty) < 0 { // we can never be below minimum difficulty
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biggest_difficulty.Set(MinimumDifficulty)
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}
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if !chain.cache_disabled {
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chain.cache_Get_Difficulty_At_Tips.Add(tips_string, string(biggest_difficulty.Bytes())) // set in cache
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}
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return biggest_difficulty
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}
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func (chain *Blockchain) VerifyMiniblockPoW(bl *block.Block, mbl block.MiniBlock) bool {
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var cachekey []byte
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for i := range bl.Tips {
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cachekey = append(cachekey, bl.Tips[i][:]...)
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}
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cachekey = append(cachekey, mbl.Serialize()...)
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if _, ok := chain.cache_IsMiniblockPowValid.Get(fmt.Sprintf("%s", cachekey)); ok {
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return true
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}
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PoW := mbl.GetPoWHash()
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block_difficulty := chain.Get_Difficulty_At_Tips(bl.Tips)
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// test new difficulty checksm whether they are equivalent to integer math
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/*if CheckPowHash(PoW, block_difficulty.Uint64()) != CheckPowHashBig(PoW, block_difficulty) {
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logger.Panicf("Difficuly mismatch between big and uint64 diff ")
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}*/
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if CheckPowHashBig(PoW, block_difficulty) == true {
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if !chain.cache_disabled {
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chain.cache_IsMiniblockPowValid.Add(fmt.Sprintf("%s", cachekey), true) // set in cache
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}
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return true
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}
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return false
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}
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// this function calculates difficulty on the basis of previous difficulty and number of blocks
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// THIS is the ideal algorithm for us as it will be optimal based on the number of orphan blocks
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// we may deploy it when the block reward becomes insignificant in comparision to fees
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// basically tail emission kicks in or we need to optimally increase number of blocks
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// the algorithm does NOT work if the network has a single miner !!!
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// this algorithm will work without the concept of time
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