This document proposes a hybrid PoW-PoS consensus protocol to prevent 51% attacks in cryptocurrency systems. The key points are: 1) A 51% attack occurs when a single entity gains over 50% of the network's computational power, allowing them to manipulate the blockchain. 2) Existing solutions have limitations like special validators, inconsistent block times, or reliance on another network. 3) The proposed solution uses PoW and PoS sequentially in each node, adjusting difficulty to maintain consistent block times. It penalizes malicious nodes and distributes profits proportionally. 4) Analysis shows the hybrid protocol maintains decentralization and the blockchain properties better than alternatives like Casper, Decred or Komodo

1. A Hybrid POW-POS Implementation Against 51%
Attack in Cryptocurrency System

2. 51% attack
If someone gains a large amount (more than 50%) of computation capability of entire network,
he can do several malicious activities in the network to manipulate the block chain for his benefit.
This kind of malicious activities are called a 51% attack.
•Fraud other users
Fake transactions
Double spending
Ruin exchanges
Liquify to fiat currency
Convert to other
cryptocurrency

3. 51% Attack Explained
Block 30 Block 31
Block 31 Block 32 Block 33
Block 32
Block 34
Block 35

4. Affects small and newly created networks

5. Investors and New Cryptocurrency Peer to Peer (P2P) Network

6. Present Solutions – Hybrid consensus protocol
P(PoW-PoS) = P(PoW) AND P(PoS)
= 51% X 51%
= (51/100) X (51/100)
= 26.01 %
P(PoW-PoS) = P(PoW) AND P(PoS)
= 71% X 71%
= (71/100) X (71/100)
= 50.41%
+

7. Present Solutions implemented by different cryptocurrencies
Dependent on another network. If other network falls then it’ll also fall.
Valid transactions could be reverted with the malicious transactions.
Transaction confirmation suffers from unwanted delays.
Peer to Peer protocol violation. No democracy and decentralization.
Miner and validator are different nodes for the same block.
Block Generation Time interval and profit distribution inconsistency.
These solutions cannot attract investors & ultimately are not suitable for new crypto
Komodo
Takes Snapshots
of their data
Stores them in
Bitcoin
Blockchain
Horizen
Delayed block
submission penalty
system
Watcher nodes for
watching malicious
activity
Decred
Voting system
Ticket distribution
At least 3/5 tickets
required
Ethereum
Casper FFG
Voting system
Deposit to be elected for
voting
2/3 votes required

8. Proposed Solution
PoW and PoS processing full cycle executes in the same thread sequentially in same node.
Difficulty target is adjusted in both cycle to maintain the block interval consistently
Defined strict spaced valid timestamp mechanism to slow down the faster nodes in the network
Block generation and Profit distribution is very accurate. Democratic and decentralized
No special validator. All nodes are equal, so P2P protocol is perfectly maintained
All the stake holders get rationally equal profit that is directly proportional to their staked asset
Nodes doing malicious activities are banned for certain period of time from the network

9. Flow Chart

10. Result
Blockchain height Block timestamp Average block time
10000 04-05-2019 12:44:32 164.72 sec
12437 09-05-2019 05:40:32 165.13 sec
15000 14-05-2019 01:18:24 164.67 sec
20000 23-05-2019 14:30:56 164.76 sec
25000 02-06-2019 03:20:00 164.75 sec
27660 07-06-2019 05:52:32 164.86 sec
30000 11-06-2019 18:12:32 165.00 sec
35700 22-06-2019 16:03:44 165.06 sec
40000 30-06-2019 21:04:32 165.05 sec
Expected block mining time: 150 + 16 = 166 sec. The first block’s mining timestamp was 15-04-2019 11:10:14.
Average block time = {(Block timestamp – first block timestamp) in seconds } / Block height

11. Results continued
Machine Configuration Staking Balance Reward Time Interval
3.5 GHz 4 CPU 8 GB RAM 10 Million coins 130 Minutes
3.5 GHz 8 CPU 16 GB RAM 10 Million coins 130 Minutes
3.1 GHz 8 CPU 32 GB RAM 10 Million coins 130 Minutes
2.8 GHz 8 CPU 16 GB RAM 10 Million coins 130 Minutes
2.8 GHz 2 CPU 3 GB RAM 10 Million coins 130 Minutes
2.8 GHz 1 CPU 3 GB RAM 10 Million coins 130 Minutes

12. Comparison
Supports
P2P
protocol
Consistent
block time
Investment
wise
proportional
profit
distribution
Autonomous
network –
Not need
any special
authority
Democratic
majority
peers are
decision
makers
Penalize
corrupted
or
malicious
user
Casper No No No No No Yes
Decred No No No No No No
PoW-PoS-PoA No No No No No No
Komodo’s dPoW Yes Yes No Yes Yes No
ZEN coin’s penalty No Yes No No Yes Yes
Proposed system Yes Yes Yes Yes Yes Yes

13. Limitations
The PoW mining loop cause processing and computing resource watage
Do not incentivize the miners according to their processing capabilities
It discourages mining pools and volunteer miners to mine in this network
Only who have some investment in this network can earn profit

14. References
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15. References continued
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16. References continued
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17. Thanks a lot for your patience