Classic two-factor authentication has been around for a long time and has enjoyed success in certain markets (such as the corporate and the banking environment). A reason for this success are the strong security properties, particularly where user interaction is concerned. These properties hinge on a security token being a physically separate device.
This paper investigates whether Trusted Execution Environments (TEE) can be used to achieve a comparable level of security without the need to have a separate device. To do this, we introduce a model that shows the security properties of user interaction in two-factor authentication.
Intel IPT has a serious issue where there is no trusted input path for the user to enter data. ARM TrustZone requires careful selection of the right components by the system-on-a-chip designer that puts the parts ofthe TEE together to guarantee that it can be trusted. An added disadvantage of TrustZone is that – unlike IPT – it does not come with a dedicated software implementation, further complicating the choices for designers of a TrustZone-based TEE.
Finally, the model also clearly shows an open problem shared by many TEEs: how to prove to the user that they are dealing with a trusted application when trusted and untrusted applications share the same display.
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