BlockChain Security Issues

What is a Blockchain?Merriam-Webster dictionary defines blockchain as,A digital database containing information (such as records of financial transactions) that can be simultaneously used and shared within a large decentralized, publicly accessible network.6 Types of Attacks on Blockchain1. 51% Attacks (Sybil Attacks)2. Double Spending Attacks3. Routing Attacks4. Private Key Security Attacks5. Selfish Mining Attacks6. Vulnerable Smart ContactsPreventing Blockchain Security IssuesUsing Proof of Stake instead of Proof of Work can help prevent the 51% attacks. As the decision will be made by users who are already in control of the majority of coins.There are a number of algorithms to prevent Sybil attacks. One of which called Proof of Work is implemented in the majority of cryptocurrencies.It is important to keep a check on the mining pools of your blockchain. Ensure that any pool that breaches a limit of 40%, gets some of its miners diverted to other pools.The use of secure routing protocols (one with certificates) can help prevent routing attacks on the blockchain.Smart contacts need to be thoroughly vetted for any bugs by experts before implementation.Build a robust community of your blockchain users and update them via emails, newsletters, etc regarding safe private key storage practices.Related Resouce - SaaS Security

什么是区块链？《韦氏词典》将区块链（blockchain）定义为：一种可在大型去中心化、公开可访问的网络中被同时使用与共享的数字数据库，可存储诸如金融交易记录一类的信息。
区块链面临的6类攻击：
1. 51%攻击（女巫攻击，Sybil Attacks）
2. 双重支付攻击
3. 路由攻击
4. 私钥安全攻击
5. 自私挖矿攻击
6. 智能合约漏洞攻击

区块链安全问题的防范措施：
采用权益证明（Proof of Stake, PoS）替代工作量证明（Proof of Work, PoW），可有效防范51%攻击。此类攻击的防范逻辑在于，决策将由已掌控多数代币的用户作出。
目前已有多种算法可用于防范女巫攻击，其中工作量证明（Proof of Work, PoW）被大多数加密货币所采用。
需对区块链的矿池实施严格监控，确保任意矿池的算力占比突破40%时，其部分矿工可被分流至其他矿池。
采用具备证书机制的安全路由协议，可有效防范区块链路由攻击。
智能合约需在上线前由专家进行全面审计，以排查所有漏洞。
搭建活跃稳健的区块链用户社区，并通过邮件、通讯简报等渠道向用户普及私钥安全存储规范。
相关资源——软件即服务（SaaS）安全