The T-Mobile Sidekick, sold elsewhere as the Danger Hiptop, ran DangerOS, which only loads software signed by Danger or a carrier. Developers used to get a signed key from a web form, but that closed in 2010 and nobody issues keys anymore. ashe, writing at x86.cx, made one instead.

The Danger SDK and a firmware flashing tool are both preserved on archive.org. Scanning the factory OS images turned up dozens of certificates, including a self-signed Developer Program root trusted by the Hiptop 1 through the Sidekick 3. It’s 512-bit RSA, issued in 2003.

Breaking it meant factoring the key with CADO-NFS, an open source number field sieve. The run used 220 CPU cores across seven machines. The rebuilt private key reproduced Danger’s own null-device-key.sq.…