A public blockchain is an open, permissionless network where anyone can join, validate, and participate according to the protocol rules. It maximises openness and decentralisation, but organisations using it must accept limited direct control over participants, governance, and data handling.
Expanded Definition
A public blockchain is an open, permissionless distributed ledger where participation is governed by protocol rules rather than organisational membership. In NHI and agentic AI contexts, the term matters when systems store references to identities, keys, attestations, or transaction logic on a network that third parties can observe and validate.
Definitions vary across vendors on how much “control” an organisation retains once data or identity artifacts are written to a public chain. The practical distinction is not whether the ledger is decentralised, but whether the organisation can enforce deletion, rotate identifiers, or constrain validator trust assumptions. That is why public blockchain use must be evaluated alongside NIST Cybersecurity Framework 2.0 and governance requirements for data minimisation, key custody, and identity lifecycle control.
The most common misapplication is treating a public blockchain as a secure place to store secrets or authoritative identity records, which occurs when teams confuse immutability with confidentiality.
Examples and Use Cases
Implementing public blockchain workflows rigorously often introduces transparency and immutability benefits while increasing exposure, operational latency, and governance complexity, requiring organisations to weigh auditability against irreversible disclosure.
- Publishing a verifiable credential hash on-chain while keeping the underlying identity document off-chain, so external parties can confirm integrity without exposing the full payload.
- Using a public chain to anchor software supply chain attestations, where the blockchain acts as an external timestamping layer rather than a storage layer for privileged data.
- Recording agent-run transaction approvals on-chain for non-repudiation, while keeping the agent’s tool permissions and secrets in a separate governed control plane.
- Extending decentralised identity patterns to users or services, then mapping those identities back to enterprise policy through off-chain controls and revocation processes.
- Referencing the lessons from the DeepSeek breach when evaluating whether public exposure of credentials, records, or backend metadata could create irreversible downstream risk.
For identity architectures, public blockchains are often paired with standards-based trust models such as the Verifiable Credentials Data Model, but no single standard governs every deployment pattern yet.
Why It Matters in NHI Security
Public blockchain design directly affects NHI security because any identity artifact, signing material reference, or agent action trail placed on-chain may become durable, visible, and hard to correct. That creates a governance burden around revocation, rotation, and selective disclosure, especially when autonomous agents or service identities are expected to operate at machine speed.
NHIMG research shows that when AWS credentials are exposed publicly, attackers attempt access within an average of 17 minutes, and as quickly as 9 minutes in some cases. That urgency is a reminder that “public” and “permissionless” are not abstract architecture labels; they translate into rapid attacker attention whenever credentials or sensitive references leak into reachable systems. The same concern appears in The State of Secrets in AppSec, where fragmented secrets management and delayed remediation weaken control over identity material.
Organisations typically encounter the consequences only after an exposed key, irreversibly published record, or disputed transaction occurs, at which point public blockchain governance becomes operationally unavoidable to address.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
OWASP Agentic AI Top 10 and OWASP Non-Human Identity Top 10 address the attack and risk surface, while NIST CSF 2.0, NIST AI RMF and NIST Zero Trust (SP 800-207) set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| NIST CSF 2.0 | PR.AC-1 | Public chains change how identity and access are asserted, verified, and limited. |
| NIST AI RMF | AI RMF addresses governance, transparency, and risk from machine-initiated actions on open networks. | |
| NIST Zero Trust (SP 800-207) | SC-23 | Zero Trust discourages implicit trust in exposed network participants or endpoints. |
| OWASP Agentic AI Top 10 | A02 | Agentic systems can misuse blockchain-connected tools and externalised actions. |
| OWASP Non-Human Identity Top 10 | NHI-02 | Public exposure of keys and identity artifacts intersects with secret management risk. |
Assume public-chain participants are untrusted and verify every identity and transaction independently.
Related resources from NHI Mgmt Group
- Why do public metadata and blockchain-linked identities increase privacy risk?
- Why do blockchain public keys create future exposure under quantum attacks?
- Why do cross-border crypto fraud cases require both blockchain analysis and public-private coordination?
- What should policy teams and compliance leaders do when seizable crypto assets are held in BTC, stablecoins, and other public blockchain balances?
