Following are the key elements of blockchain technology and their value. Other technologies can be blockchain-like if they have some of these elements, but are not considered true blockchains.

• A tamper-evident “ledger” (linear, append-only) data structure

• Valuable for recording events that definitely happened

• Less valuable for recording any information that is uncertain or required to be deleted (such as personal information for which a “right to be forgotten/right to erasure” has been established)

• Autonomous, distributed, and possibly even decentralized (no node has higher privileges) storage nodes

• Valuable for architectures where trust in a central authority is difficult or undesirable to establish (although trusted third parties do play a role in some blockchain deployments anyway; see third bullet below)

• Less valuable for recording sensitive information because of the increased attack surface (every node has a copy of everything) and resulting increased privacy considerations

• Less valuable for recording voluminous information because every node has a copy of everything

• Mathematically based (algorithmic) consensus for contents of new ledger entries

• Valuable for incentivizing cooperative behaviors among node participants about entry contents (“proof of work” as used in Bitcoin is the most famous)

• Less valuable if other parts of the “BLT sandwich” (business-legal-technical) are not well controlled for through IAM, trust frameworks, etc. -- e.g., multiple node participants can collude to game the system -- but then decentralization goals can be compromised thereby