A new keybox technique is public, and Duck ToolBox already implements it
A new route to an attestation keybox has been published, and it differs from both routes people knew before. It does not extract the device's CDI_Leaf seed from the TEE for unlimited offline signing, and it does not rely on any external service. The core idea is to treat the device's KeyMint TA as a signing oracle: the real device runs the certificate request itself, and we only supply the software public key we want it to sign.
Concretely: the host generates a P-256 key pair and keeps the private half. The public half goes into the TA's CSR_V2 request (command 0x3122), and the trusted application signs it with the device's genuine DICE chain. That yields a completely legitimate CSR, which is then submitted through the normal fetchEekChain / signCertificates flow to Google in exchange for a certificate chain. Finally the private key and the chain are assembled into a keybox.xml that Tricky Store can load. Nothing is extracted, and the bootloader is never touched. The full walkthrough is at the Kanxue write-up linked below.
Duck ToolBox reduces that chain of steps to two commands. Start with rkp-device status, which checks the prerequisites: Android arm64, root, /dev/smcinvoke, the keymaster library, and a Qualcomm SoC. It names exactly what is missing instead of leaving you to guess. When the checks pass, provision --acknowledge-limitations produces keybox.xml, the CSR, the DER certificate chain, and the private key. The tool is strict about what it accepts: the issued leaf certificate must carry the public key it generated, the chain must be one complete leaf-to-root path with no stray certificate, and any failure is rejected before a single file is written. What it does write is checked against Tricky Store's own keybox validator, so the artifact is one the device will actually load.
The boundaries matter, so: it depends on Qualcomm's KeyMint vendor ABI and therefore works on some devices only; when the ABI does not match you get an explicit error saying the firmware may be incompatible rather than a silent failure. It issues RKP certificates only, with no test or software attestation keys. Beyond writing the artifacts it changes no device state. The keybox is tied to a key generated on the device, so it is valid there and nowhere else: keep the private key file. The prerequisite check is read-only and side-effect free, so running it first to see whether your phone qualifies is the sensible way to start.
And yes, it is completely free: no extra hardware, no account, no server. The underlying method comes from a research write-up on the Kanxue forum:
https://bbs.kanxue.com/thread-293244.htm — the implementation is Duck ToolBox's, the credit for the method belongs to its author. If you run it on real hardware, your results are welcome; they help us describe the compatible range accurately.
