Blockchain security

What is blockchain?

February 18, 2021 by Greg Belding

What is Blockchain?

Blockchain is built from layers rather than in one big piece. Cryptographic algorithms and data structures are part of the lowest layer of blockchain technology. Blockchain blocks hold information like metadata and transactions. Hashes are used  to bind blocks. These hashes constitute the chain in blockchain. Once a blockchain is set it is hard to modify. Blockchain uses public keys like in asymmetric cryptography but if the cryptography is effective, the first layer should be secure.

Blockchain consensus likes to create party unity without a central digital ledger. Blockchain uses consensus algorithms but the algorithms are flawed. Blockchain security can fail, allowing outside entities to take control of a blockchain network. Blockchain is entirely dependent upon security that uses cryptographic algorithms and protocols. It doesn’t trust individuals or a centralized digital ledger. 

Asymmetric Cryptography

Having a strong hash function is critical. It’s nearly impossible to find blocks with the same hash value. This is because the header of the last block is stored in the next block. So, if someone wants to create a fake individual block, they have to also create all of the blocks that come after it, which is very difficult. Asymmetric cryptography, also known as public-key, works because two keys are related. The public side of the cryptography provides the decryption. The private key is responsible for decryption and the generation of a signature. Malicious nodes are prevented from mischief by digital signatures. It’s not possible to make a fake block or transansaction and blame it on someone else without a correct digital signature. 

Hash Functions

Hash functions are used for a number of reasons in blockchain. They help make sure functions only flow one way and resist collisions. Collision resistance says it doesn’t matter what two inputs go into a hash function they won’t create the same output.  The bottom layer of blockchain is an assembled group of cryptographic algorithms and data structures that form the blocks that is the very basis of blockchain. This allows blockchain to work as it is intended to do while maintaining security. Algorithms play a big role at the bottom level so any successful attack means the cracking of algorithms or the seemingly random implementation error. 


Blockchain architecture exists to distribute digital ledgers but they aren’t the only game in town. Other architectures attempt to fill the gaps where blockchain ledgers are limited. These can include limits of scale and speed. Sidechains use pegging to push beyond the basic blockchain and take it to the next level. Pegging allows for the support of crossing chains and swapping within single blockchains. Sidechains are multiple blockchains that are each singular but linked somehow. While blockchains and sidechains have similar security problems, sidechains, in particular, have a greater vulnerability in the links between chains. 



  1. /topic/introduction-to-blockchain/
  2. /topic/blockchain-security-overview/
  3. /topic/blockchain-technology/
  4. /topic/fundamentals-of-blockchain-security/
  5. /topic/blockchain-beyond-the-basics/


Posted: February 18, 2021
Greg Belding
View Profile

Greg is a Veteran IT Professional working in the Healthcare field. He enjoys Information Security, creating Information Defensive Strategy, and writing – both as a Cybersecurity Blogger as well as for fun.