The Important

  • Blockchain is not a database.
  • Blockchain is a journal.
  • Blockchain is best used to record immutable information
  • Blockchain should not be used for mutable information
  • Blockchain does not provide anonymity1, transaction partners are known
  • Blockchain does provide confidentiality, specifics of records can be hidden

Note (1):

  • The traceability of criminal behavior has nuances.
  • There are both public and private blockchains with different characteristics


There are many layers of the Internet that security, privacy, and data integrity are concerns. There are the approaches we build to transporting bits that reduce packet loss and packet corruption, there are the resend capabilities of TCP, and there is, of course, the application layer itself.

The events of the last decade have shaken our confidence in the efficacy of information, the role of state and non-state actors, and our overall trust. There have been protests, government hearings, and more. As the world looks to a new era of Internet trust, there are many approaches and technologies competing for a place in that conversation. One of those technologies is blockchain, which is no longer a new technology, and one that many readers are likely already familiar with.

Blockchain is a technology that has gained mindshare for recording immutable data, like transactions, where the data does not change, there is the elimination of a central controlling entity, good confidentiality, and good protection against fraud and tampering.

While blockchain is being considered for many roles, cryptocurrency is to date, its most famous use case. The immutable transactional nature of financial records being a good match for the qualities of Blockchain. Not all things done on the Internet are a good fit for Blockchain, especially true add, change, update, delete databases.

This is a social conversation with a large scope, but it is a conversation that is growing and likely will not be deafened. Below are some of the pros/cons of Blockchain.

Before going into the details of blockchain, it is worth noting there are two types of blockchain, private and public.

Private BlockchainPublic Blockchain
Permission basedPermissionless
Who can participateAuthorized entitiesAnyone
Number of nodesLowHigh
Transaction ratesHighLow
Consensus algorithmsYesNo
HackableHigher than publicLow to impossible
Energy usageLowHigh
Complete replica of the ledgerYesYes
Append-only ledgerYesYes
Table 1. Private Blockchain vs Public Blockchain

What happensUpsideDownside
Hundreds to millions of computers perform the same blockchain approval calculationAccuracy:   A single calculation error unlikely to be retained by the block chain.  Inefficiency / cost: Significant compute and energy resources are used to add a single block to the block chain. In aggregate, the resources used can be staggering. Even at an individual node level, the cost can be significant.
Hundreds to millions of computers have a copy of the blockchainTamper resistant: Difficult to tamper with all copies of the blockchain. Both a computational error or a deliberate tampering would require that 51% of all participating nodes be impacted. As the number of blockchain participants increases, the probability of this decreases. As the amount of processing performed by one entity increases, the value of the blockchain decreases, which becomes a deterrent to 51% control of the blockchain. Some researchers do claim though that now criminals can rent computational resources, rather than having to purchase them, it may become easier to get 51% control. It still requires enormous computing resources to change blocks that have been on the chain for a long time, so experts believe only the most recent blocks would be exposed and that the blockchain would adapt to the threat. 51% attacks are an area of mostly theory with little real-world experience to judge them by. No single point of failure: A traditional database may be more vulnerable to technical failures in one or a few servers. Inefficiency / cost: Significant storage and energy resources are used to store all copies of the blockchain, with the potential for a blockchain exceeding the storage capacity of some participating nodes.
Peer to peer elimination of a centralized entityReduced Fees: The potential for “middle-man” fees to be reduced. Security / privacy: No centralized entity monitoring.Potential information loss: The potential for private information to be lost forever, if a private key is lost. In the case of a cryptocurrency, this could also mean loss of currency.
A block can be added any time or day the verification process can be completed.Continuous update:  No waiting for weekend or overnight blackout periods to end. Low-velocity updates:  The number of transactions per second is commonly many orders of magnitude less than traditional transaction systems
Transactions are not anonymous, they are confidentialPrivacy: Private/personal information remains confidential.Identity & Illegal activity Public key is obtainable identity information Privacy is considered to also create the right conditions for illegal activity.
Each block in the block chain contains a unique hash of the block, and a hash of the preceding blockImmutability/security: Once a block is added to the blockchain it is difficult to change, because all the blocks that come after it have to also be changed. The longer the blockchain, the more computationally intensive this becomes. This is a good characteristic for records that are not meant to change, and for anything that requires an audit trail.Immutability: While this is a good characteristic, if data or code does need to change, it can require abandoning one chain and taking up a new chain
Open Source  Transparency: While personal information remains private, how the code works is transparent and public. 
Private-public cryptographic signature verificationRobust verification:Every node verifies the authenticity of the user.Complexity: Every node using an algorithm like ECDSA (Elliptic Curve Digital Signature Algorithm) to ensure that the transaction happens between the correct nodes, is asserted by some, to be tricky and complex.
New paradigmNew benefitsIntegration challenges with existing approachesRegulation gaps and scamsLack of inhouse skills for EnterprisesLack of understanding by consumers
Publicly viewable transaction ledgersTransparencyLack of privacy Especially for enterprises (which is leading to improvements in private transaction options and use-specific authentication, see permissioned blockchain, example Hyperledger and Corda).
Table 2. How blockchain works, pros and cons

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