Canon's image signing scheme was half-assed and was comprehensively broken, they didn't even store their signing keys on a secure element:

https://www.digitalartsonline.co.uk/news/creative-lifestyle/...

>In Canon's second version of its ODD system, the HMAC code is 256 bits. The code is the same for all cameras of the same model. Knowing the HMAC code for one particular model allows the ODD to be forged for any camera within that model range, Sklyarov wrote