Blockchain technology offers desirable decentralized features, immutability, integrity, anonymity, and fault-tolerance in trustless environments. The increasing popularity of blockchain technology in many fields also raises security concerns. Albeit the blockchain technology comprises fundamental security features, the blockchain meets some security issues based on the type of application. Different types of blockchain security algorithms are introduced in many literature surveys. Among them, the consensus algorithms receive significant attention, as it assists diverse investors and minors in accomplishing a common agreement based on the existing states of immutable ledgers. The blockchain security risks are listed as follows.
   •  Network related attacks
   •  Security at endpoints
   •  Intentional Misuse
   •  Vulnerabilities of codes
   •  Protecting the block data
   •  Negligence of Humans
  The security algorithms to meet the security risks of blockchain are as follows.
   • Consensus Algorithms
     •  Proof of Work (PoW)
     •  Proof of Stake (PoS)
     •  Delegated Proof of Stake (DPoS)
     •  Proof of Elapsed Time (PoET)
   •  Cryptographic Solutions
     •  Digital Signatures
     •  Hashing
   •  Peer-to-Peer Network Protocols
   •  Proofs with Zero-Knowledge