Home / Knowledge hub / Hardware security module (HSM)
Knowledge hub
Hardware security module (HSM)
A tamper-resistant device that holds keys and does cryptography inside it.
What it means
A hardware security module, or HSM, is a dedicated device built to store cryptographic keys and perform operations such as signing and decrypting inside it. The keys are created in the device and are designed never to leave it in the clear. It can be a physical box, a card, or a cloud service.
Your application does not read the key. It sends data in and gets a result back, such as a signature. If the application server is compromised, the attacker cannot simply copy the key file, because there is no key file to copy.
Why it matters
Some keys are worth far more than the servers around them: a payment key, a code-signing key, the root of a certificate authority. A stolen copy lets an attacker sign or decrypt anything, anywhere, for as long as the key lives. An HSM makes theft of the key itself much harder.
Standards often name them. Validation under NIST's FIPS 140 programme gives buyers a recognised way to judge a device, and payment and certificate authority rules expect keys of certain types to be held in one. Cloud key services offer HSM-backed options without owning hardware.
How it shows up
You meet HSMs in payment systems, certificate authorities, code signing, database encryption and cloud key management. Apps call them through standard interfaces, and access is controlled by roles and credentials. Many are used to hold a master key that protects other keys, as in envelope encryption.
Know the limit. An HSM guards the key, not the application using it. If an attacker takes over the app, they can ask the HSM to sign or decrypt whatever they like, without ever seeing the key. Restrict who and what may call it, log every use, plan key rotation, and keep a backup plan for when a device fails.
Questions people ask
Hardware security module (HSM), answered
Do we need a physical HSM?
Often not. Cloud providers offer managed key services, some HSM-backed, which meet many needs at lower cost and effort.
Physical devices suit high-assurance or regulated uses. Choose by the sensitivity of the key.
What does FIPS 140 mean for an HSM?
FIPS 140 is a US and Canadian standard for cryptographic modules, now at version 3. A validated module has been tested against it by an accredited laboratory.
Check the level and the exact version of the device.
Does an HSM make our app secure?
No. It protects the key, not the code that asks it to use the key. A flaw in your application can still misuse the key.
Control who may call the HSM and log each use.
What happens if the HSM fails?
You need a backup. Most designs use clustered devices or approved backups of the key under strong controls.
Test restoring before you rely on it. A key you cannot restore is a key you may lose.
How is an HSM different from a secrets manager?
A secrets manager stores and hands out secrets such as passwords or API keys to applications. An HSM keeps keys inside hardware and does the cryptography itself.
Many systems use both.
Sources
Where this comes from
Related
Terms that sit next to this one
Cloud key management
Using the provider's managed service to create, store and rotate encryption keys.
Key rotation
Replacing a credential on a schedule so a leaked one has a short life.
Envelope encryption
Encrypting data with a data key, then encrypting that key with a master key.
Secrets management
Keeping keys, passwords and tokens out of code and in a vault.
Digital signature
A value that proves who produced data and that it has not changed since.
Who can ask your keys to sign?
A key in an HSM is only as safe as the app that calls it. We check whether a signed-in account can reach functions that sign or decrypt on its behalf, and prove it with the request and response. Book a pilot.
Or start with a $199 pilot on one application: thirty days, success criteria agreed before day one, credited against the annual if you convert.