Communication Logic

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The Cuvex BIT device does not establish a direct communication channel with the Cuvex app.

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Instead, the device dynamically creates an external USB storage unit, which the smartphone and the app use to exchange files. Functionally, the device behaves like a virtual USB flash drive.

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This storage unit:

• Is named “Cuvex”

• Contains an internal folder also named “Cuvex”

• Is automatically created and unmounted by the device for each process that requires it

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For the app to read or write data, the user must explicitly authorize access to this storage unit and to the “Cuvex” folder through the smartphone’s operating system file manager.

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Operation is equivalent to connecting an external USB flash drive to the smartphone, with the difference that:

• The flash drive is named Cuvex

• The shared folder is named Cuvex

• Control is governed by the Cuvex BIT device itself

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Workflow Initiation Recommendations

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Workflows that should be initiated on the Cuvex BIT device

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It is recommended to initiate from the device itself any workflows that require the USB storage unit to be mounted in advance, such as:

• Firmware updates

• Cryptogram decryption

• PSBT transaction signing

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When these processes are initiated from the device, it automatically creates the storage unit and shared folder and then waits for the app to write the required data.

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Workflows that can be initiated directly on the device

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Processes such as:

• Secret encryption

• Bitcoin wallet creation

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can be initiated directly on the device. Once completed, the app can access the created shared folder to retrieve the corresponding information.

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In all cases, both the app and the device guide the user, indicating when it is necessary to initiate the process on the other end and when to authorize read/write access. The workflow is designed to be clear and unambiguous.

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Operational Summary

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• All functional workflows of the Cuvex BIT and the original Cuvex device are equivalent.

• The only difference lies in the data import and export method.

• On the original Cuvex, cryptograms were exported via NFC.

• On the Cuvex BIT, cryptograms are exported via USB-C to the Cuvex app, where they:

  • Are stored in the smartphone’s secure element

  • Can be cloned to:

    • NFC cards (cryptograms without biometrics only)

    • External USB-C storage devices (all cryptogram types)

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Communications are fully isolated, since:

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• There is no direct App ↔ Device communication channel

• Only files are exchanged through a folder governed by the Cuvex BIT device itself

• Exchanged data is either encrypted or consists of non-sensitive metadata