Question about asymmetric encryption DFU

[Eugene]

We have created a firmware and encrypted it with a private key and made it public. When we download it to the chip it's decrypted with a public key stored in the chip. Right? What adnventages does it offer vs. standart symmetric encryption?

[Wojtek]

If you are using signing tools from newest SDK, it doesn't encrypt your firmware! If I understand correctly, there is only a checksum (sha-256) of the firmware, that is signed (by your private key) and verified on the chip (by verification - public key). there is no encryption there. So if you are worrying about decompilation of firmware, that is not the solution. It only protects your chip from unauthorized DFU updates (which may brick your device or something)

[Vidar Berg]

DFU signing ensures that an image is received from a trusted source, but doesn't encrypt it as Wojtek mentioned. The advantage with asymmetric over symmetric signing is that it's safer because only the public key will be stored on the nRF device, while the drawback is increased complexity.