From fc71a260a8aeadae166f419e5127a6ab751c2132 Mon Sep 17 00:00:00 2001
From: Yilun <zyl.skysniper@gmail.com>
Date: Wed, 21 Jul 2021 00:31:56 -0700
Subject: [PATCH] Add weight when selecting sigchain miner for better security

Signed-off-by: Yilun <zyl.skysniper@gmail.com>
---
 cmd/nknd/nknd.go |  2 +-
 config/config.go |  8 ++++++++
 pb/sigchain.go   | 14 +++++++++++++-
 3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/cmd/nknd/nknd.go b/cmd/nknd/nknd.go
index 8b75cf154..adecb25b9 100644
--- a/cmd/nknd/nknd.go
+++ b/cmd/nknd/nknd.go
@@ -47,7 +47,7 @@ import (
 )
 
 const (
-	NetVersionNum = 25 // This is temporary and will be removed soon after mainnet is stabilized
+	NetVersionNum = 26 // This is temporary and will be removed soon after mainnet is stabilized
 )
 
 var (
diff --git a/config/config.go b/config/config.go
index d21bb6d3f..a92d0f82c 100644
--- a/config/config.go
+++ b/config/config.go
@@ -224,6 +224,14 @@ var (
 		heights: []uint32{2900000, 0},
 		values:  []bool{true, false},
 	}
+	SigChainMinerWeightBase = HeightDependentInt32{
+		heights: []uint32{2900000, 0},
+		values:  []int32{2, 1},
+	}
+	SigChainMinerWeightMaxExponent = HeightDependentInt32{
+		heights: []uint32{2900000, 0},
+		values:  []int32{4, 0},
+	}
 )
 
 var (
diff --git a/pb/sigchain.go b/pb/sigchain.go
index 8c3c48022..2358829a5 100644
--- a/pb/sigchain.go
+++ b/pb/sigchain.go
@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"math"
 	"math/big"
 
 	"github.com/nknorg/nkn/v2/common"
@@ -222,7 +223,18 @@ func (sc *SigChain) GetMiner(height uint32, randomBeacon []byte) ([]byte, []byte
 				index: i,
 				elem:  e,
 			}
-			minerElems = append(minerElems, t)
+			base := config.SigChainMinerWeightBase.GetValueAtHeight(height)
+			exp := int(config.SigChainMinerWeightMaxExponent.GetValueAtHeight(height))
+			if exp > i-1 {
+				exp = i - 1
+			}
+			if exp > sc.Length()-2-i {
+				exp = sc.Length() - 2 - i
+			}
+			count := int(math.Pow(float64(base), float64(exp)))
+			for i := 0; i < count; i++ {
+				minerElems = append(minerElems, t)
+			}
 		}
 	}
 	elemLen := len(minerElems)