Host Card Emulation for Mobile Payments: Today’s Challenge

Host Card Emulation (HCE) is a new alternative approach to mobile payment security where critical payment credentials are stored in a secure shared repository rather than in a Secure Element inside the phone. A summary of the role of Thales HSMs in the HCE ecosystem can be found below.

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Securing a mobile phone such that it can be used to make credit or debit transactions at a physical point-of-sale (POS) terminal is a challenge. Payment systems based on magnetic stripe cards have evolved to use EMV chip cards and the natural next stage was to utilize dedicated security hardware inside most phones called a Secure Element to host the payment application, user payment credentials and the associated cryptographic keys.

However, this approach has proven difficult to take from pilot to mass deployment for a variety of reasons – lack of standardization for mobile phones, complex certification requirements and most importantly the reluctance of many banks to cede control to a third party, the Trusted Service Manager (TSM). In the TSM model the bank pays to ‘rent space’ on the Secure Element which is typically controlled by a mobile network operator (MNO) or handset manufacturer. To overcome these challenges an alternative approach is rapidly gaining support - host card emulation (HCE). With HCE, critical payment credentials are stored in a secure shared repository (the issuer data center or private cloud) rather than on the phone. Limited use credentials are delivered to the phone in advance to enable contactless transactions to take place. Although this eliminates the need for TSMs and shifts control back to the banks, it brings with it a different set of security and risk challenges.  Click to download our HCE white paper.

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More about Host Card Emulation

Host Card Emulation was kick-started by Google in late 2013 with the Android 4.4 Operating System (OS) release, codenamed KitKat. This enabled any application on phones for the first time to communicate directly with the NFC controller and hence interact with a contactless POS terminal. Prior to this innovation, all NFC communications required participation by the Secure Element under MNO control. This critical change enables issuing banks to offer contactless mobile payment applications on the latest Android phones without needing business relationships with MNOs. MasterCard and Visa formally endorsed the HCE concept via separate press releases in February 2014 when they also announced plans for associated specifications. In the early days of HCE (when standards and certifications are being developed) it is likely that transaction values will be small to limit risk but pressure to increase will be strong and it will be critical that system security can support this. The challenge will be to get the balance right between security, risk and the quality of the user experience.

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Risks Associated with Host Card Emulation

  • The establishment of a centralized service to store many millions of payment credentials or create one-time use credentials on demand creates an obvious point of attack. Although banks have issued cards for years those systems have largely been offline and not requiring round-the-cloud interaction with the payment token (in this case a plastic card). Host Card Emulation requires these services to be online and accessible in real-time as part of individual payment transactions. Failure to protect these service platforms places the issuer at considerable risk of fraud.
  • Although the phone no longer acts as the store for payment credentials it still plays three critical security roles. All three create opportunities for theft or substitution of credentials or transaction information.
    1. It provides the means for applications to request card data stored in the HCE service
    2. It is the method by which a user is authenticated and authorizes the service to provide the payments credentials
    3. It provides the communications channel over which payment credentials are passed to the POS terminal
  • All mobile payments schemes are more complex than traditional card payments and yet smart phone user expectations are extremely high. Poor mobile network coverage makes HCE services inaccessible, complex authentication schemes lead to errors and software or hardware incompatibility can bring everything to a halt. A flexible approach will be required where credentials are cached and risk-based approvals will become the norm all at a time when standards will be maturing and the need for certifications will be imposed.

Host Card Emulation Mobile Payments: Thales e-Security Solutions

Thales e-Security hardware security modules (HSMs), both nShield and payShield, are in use today helping to secure HCE-based solutions. Payment credentials are securely generated and stored centrally using HSMs by the issuer who also has the flexibility to decide how many keys are stored in the phone at any given time and therefore cover situations where offline authorization is supported as part of the issuer risk decision. In an online authorization situation (which is the usual deployment mode for HCE solutions) the issuer uses HSMs to validate the cryptogram which is generated by the phone app in real time as part of the contactless mobile payment transaction. In this case the security design of the phone app is critical to ensure that the processing inside the phone limits the risk of key or sensitive data exposure to fraudulent attack. That is why the card schemes are conducting extensive validation of mobile payment app security (which includes the interface to the issuer involving HSMs) before the bank can go live with the HCE service.

Benefits

  • Use the same types of Thales HSMs for HCE that are used globally today for authorizing card payments and issuing EMV cards
  • Take advantage of the Thales integration partner ecosystem to source proven HCE-based solutions and be automatically compatible with the latest card scheme specifications
  • Choose from a range of cryptographic algorithms and key management schemes already supported by Thales HSMs to create a hardware-based secure session between the issuer system and the phone, eliminating man-in-the-middle attacks during the credential loading process
  • Leverage the existing HSM certifications, FIPS 140-2 level 3 and/or PCI HSM, to simplify audit compliance and ensure the best possible key generation and protection methods are deployed