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Right now our DeviceCheck machinery only works on real iOS devices (excluding the iOS simulator) and Android devices (real or emulator) and we need them to work for the web (for the web version of Multipaz Wallet) and it would also be nice if they worked for the iOS simulator. As such, introduce `DeviceAttestationSoftware` which can be generated in any environment which lacks hardware-backed attestation. This is inherently insecure but the backend has access to the attestation so it can provide a subset of functionality to e.g. web clients. For example, for Multipaz Wallet we can allow access to shared state (bound to e.g. a Google account) for web clients but refuse access to e.g. key attestation services. Also introduce the notion of a "proof of secret" embedded in this new attestation. This is inhererently insecure (an attacker can exfiltrate this client-side secret from the binary or app process) and HW-backed attestation should be preferred but in an environment without HW-backed attestation this adds a little bit of security. Change DeviceCheck for JVM so it uses `DeviceAttestationSoftware` and also DeviceCheck for iOS when running on the iOS simulator. This way it's actually possible to develop Multipaz Wallet using the iOS simulator when using its dev backend configured to accept software attestations. Add a new screen to Compose TestApp to easily test both device attestations and assertions, both strict and non-strict. This also uncovered a bug in `ClientRegistrationImpl` where we would always generate empty challenges. Fix this. Test: Unit tests for DeviceAttestationSoftware. Test: Manually tested on Android and iOS. Signed-off-by: David Zeuthen <zeuthen@google.com>
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sorotokin
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Mar 30, 2026
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Right now our DeviceCheck machinery only works on real iOS devices (excluding the iOS simulator) and Android devices (real or emulator) and we need them to work for the web (for the web version of Multipaz Wallet) and it would also be nice if they worked for the iOS simulator.
As such, introduce
DeviceAttestationSoftwarewhich can be generated in any environment which lacks hardware-backed attestation. This is inherently insecure but the backend has access to the attestation so it can provide a subset of functionality to e.g. web clients. For example, for Multipaz Wallet we can allow access to shared state (bound to e.g. a Google account) for web clients but refuse access to e.g. key attestation services.Also introduce the notion of a "proof of secret" embedded in this new attestation. This is inhererently insecure (an attacker can exfiltrate this client-side secret from the binary or app process) and HW-backed attestation should be preferred but in an environment without HW-backed attestation this adds a little bit of security.
Change DeviceCheck for JVM so it uses
DeviceAttestationSoftwareand also DeviceCheck for iOS when running on the iOS simulator. This way it's actually possible to develop Multipaz Wallet using the iOS simulator when using its dev backend configured to accept software attestations.Add a new screen to Compose TestApp to easily test both device attestations and assertions, both strict and non-strict.
This also uncovered a bug in
ClientRegistrationImplwhere we would always generate empty challenges. Fix this.Test: Unit tests for DeviceAttestationSoftware.
Test: Manually tested on Android and iOS.