Private keys remain dominant because they directly control asset transfer and often sit at the center of trust and access. When attackers obtain a key, they can bypass many application controls, impersonate legitimate operators, and move funds quickly. Centralized services are especially exposed when keys are reused, poorly protected, or accessible to too many systems or staff.
Why private keys stay the preferred theft target
Private keys are still the highest-value target because they do not just unlock a system, they authorize value transfer. In practice, that makes them the shortest path from access to monetization. A stolen key can bypass application-layer checks, inherit whatever permissions the holder had, and let an attacker move funds before defenders can intervene.
The problem is amplified by how keys are used in real environments. They are often copied into multiple services, embedded in automation, or accessible to operators and integrations that do not need full custody. Once a key is reusable and broadly trusted, theft becomes more efficient than trying to defeat every downstream control one by one.
That pattern is consistent with NHIMG’s The 52 NHI breaches Report, which shows how credential theft, exposed secrets, and broad trust relationships repeatedly lead to compromise. For the same reason, compromised non-human identities remain a dominant breach path in NHIMG’s Ultimate Guide to NHIs: when secret material is the effective bearer of authority, theft is enough.
What makes stolen keys more effective than other attack paths
Keys are attractive because they are both authentication material and operational authority. If an attacker gets the right private key, they often do not need to escalate through passwords, MFA prompts, or user interaction. They can act as the legitimate holder, which is especially powerful in centralized services where one compromised key may govern many wallets, workflows, or service endpoints.
Attackers also favor keys because they are fast to exploit and easy to automate. A valid key can be tested, reused, and traded quickly, while the victim may not notice until funds are gone or signing activity looks “normal.” The risk grows when key material is stored outside hardened custody, shared across environments, or left valid for long periods after an access relationship should have ended.
That operational reality is reflected in published breach reporting from NHIMG’s Ultimate Guide to NHIs, including the statistic that 96% of organisations store secrets outside secrets managers in vulnerable locations, and 97% of NHIs carry excessive privileges. Those conditions make stolen keys not just useful, but disproportionately effective compared with weaker or slower fraud paths.
Risk and Threat Considerations
Once a private key is exposed, the main risk is not only theft, but irreversible authority transfer. In crypto systems, that usually means the attacker can sign as the rightful controller, drain assets, and often do so faster than detection, because the transaction itself can look valid on-chain.
Failure mechanism: The key is reused, overprivileged, copied into too many systems, or left in a place where compromise of one endpoint yields full signing authority. From there, the attacker bypasses higher-level controls and uses legitimate cryptographic trust to move funds or rotate access against the victim.
Impact: Losses are immediate and usually hard to reverse, especially for centralized custodians or high-volume services where one key may guard many assets. The same exposure also increases incident scope, because a compromised key can enable follow-on access, impersonation, and broad trust abuse beyond the initial theft.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
OWASP Non-Human Identity Top 10 and MITRE ATT&CK address the attack and risk surface, while CIS Controls v8 and NIST CSF 2.0 set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| OWASP Non-Human Identity Top 10 | NHI-01 — Secret Sprawl and Exposure | Private keys behave as high-value secrets whose exposure directly enables theft. |
| NHI-03 — Excessive Privilege | A stolen key is most damaging when it inherits broad signing authority. | |
| NHI-04 — Lifecycle and Rotation | Expired or long-lived keys stay usable long after they should have been revoked. | |
| Recommendation — Minimise private key exposure and keep signing material out of broad-access storage. Constrain each key to the narrowest possible signing scope and blast radius. Rotate and revoke private keys on a defined lifecycle, not only after suspected compromise. | ||
| CIS Controls v8 | 6.3 — Access Rights Management | Private-key theft is amplified when access paths are excessive or poorly reviewed. |
| 3.4 — Secure Configuration for Storage of Confidential Information | Keys are often stolen from insecure storage locations and tooling. | |
| Recommendation — Review and remove unnecessary access paths that can reach key material or signing systems. Store private keys only in hardened protected locations with restricted retrieval. | ||
| NIST CSF 2.0 | PR.AC — Access Control | The issue is fundamentally about controlling who or what can exercise authority through a key. |
| PR.DS — Data Security | Private keys are sensitive data whose confidentiality directly determines asset security. | |
| ID.AM — Asset Management | You cannot defend stolen keys well without knowing where key material exists and who depends on it. | |
| Recommendation — Restrict key use to approved systems, operators, and signing workflows. Protect private key material with encryption, segregation, and controlled handling. Maintain an inventory of all private keys, where they live, and what they can access. | ||
| MITRE ATT&CK | T1552 — Unsecured Credentials | Stolen private keys are a form of credential access that attackers seek from insecure storage. |
| Recommendation — Hunt for exposed key material in repositories, endpoints, and automation systems. | ||
Practitioner Guidance
What to verify: Treat any private key with broad signing authority as a high-risk asset if you cannot prove where it is stored, who can access it, and whether it is still needed. If the answer includes shared custody, long-lived validity, or cross-environment reuse, the exposure is already material even before any theft signal appears.
Decision rule: If a key can move funds directly, prioritise rotation, privilege reduction, and custody review ahead of broader forensic curiosity. The practical question is not whether an attacker “used the key cleverly,” but whether the key was allowed to represent too much authority for too long.
Practitioner takeaway: Private keys dominate because they collapse access, authority, and monetization into one artifact, so the most important control objective is to reduce what any single key can do and how long that authority remains valid.
Related resources from NHI Mgmt Group
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Reviewed and updated by the NHIMG editorial team on September 19, 2026.
NHI Mgmt Group — the #1 independent authority on Non-Human Identity, IAM, and Agentic AI security. nhimg.org
