A hardware security module (HSM) is a device that provides a secure and dedicated environment for performing cryptographic operations thus reducing the likelihood of secret key material being compromised as well as improving cryptographic processing performance. Here we try to address the secret key protection aspect of using HSMs.
Confidential electronic keys, such as those used by the PKI private key are critical to application security. If their confidentiality is compromised, a fraudulent message purporting to be from a legitimate user can be sent to another user. The receiver of such a message may not be able to detect this fraud, because the signature appended to the message would appear to be valid. Accordingly, it is critical that confidential keys be adequately protected.
The first step to protecting confidential keys is to have good controls on access to environments where the keys are created and where they reside. For additional protection, one approach is to employ various software techniques to secure the keys on the host computer where the keys reside, and where they are used for cryptographic operations. Typically, the keys are encrypted on disk, and memory protection measures are employed to protect the key during cryptographic operations. Additionally, encryption and other measures can be used to protect keys when they need to be transported to another host computer.
Although software-based approaches can offer significant additional protection, an even greater level of security is possible by employing hardware devices, such as HSMs, that are specifically designed to protect confidential electronic keys. Typically, these devices are used to safe-store keys. The keys are created in these devices and cryptographic operations performed with these keys can be carried out within these devices, thus making sure that the keys never need to leave the hardware. Various physical and logical security features of these devices further minimize the risk of key compromise.
If a user’s private key were only protected by a software-based approach, a successful attack could occur if there were co-ordinated security breaches at two customer institutions or two branches of an institution. Such an attack would be relatively difficult but not impossible. Use of an HSM instead of software-based protection would likely make this attack more difficult since it is harder to steal HSM private key information without being detected.
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