Demystifying Hardware Security Modules

Hardware Security Modules or HSMs are physical hardware devices used to keep keys for digital encryption safe, secure and tamper and theft proof.

HSMs can generally be classified as SSL, Payment and Point-to-Point Connection types.

SSL HSM

• SSL HSM is used for storing private keys and keeping private keys really private whereby they remain inside the box at all the times. For every SSL request, the servers will establish communication with SSL HSM to validate the request.
• An SSL HSM can typically store up to 2 million private keys.
• An SSL HSM is very secure as it does not allow memory scrapping and the keys are safe even if the machine gets owned by the hackers. The configuration can be cumbersome though with the source code to be compiled and put into production yourself.
• SSL HSM is available as a standalone device over the network or PCI Express card.

Payment HSM

• Payment HSM is a hardened tamper-proof hardware device used for symmetric encryption for payment processing.
• They are typically used for all phases of credit card life cycle i.e. from PIN verification to generation of EMV keys
• One HSM typically stores one Master key and all generated keys are encrypted with it.
• The Master key is typically stored on three key cards with each card being held by a separate custodian. Each custodian should have a back up, so to affect Master key ceremonies, at least 6 stakeholders need to be involved. Re-configuration of the Master key would need two physical keys to be inserted into the device and it will disconnect the device from the network. Additionally, all the custodians with three separate key cards must be available for re-configuring the Master key.
• For a stable production environment, at least three HSM devices will be needed to run as Primary, Secondary and Disaster Recovery modules.