Certificate validation on an IoT device using few bytes I'm trying to validate if an IoT device is authentic or it's a fraud. The problem is I only have 17 bytes to do that verification.

What if I let the IoT device sign the message with the private key and the client will check in a server if that message was signed with the correct private key like the RSA algorithm.

But the problem is that I don't think only 17 bytes is secure. I'm asking if you guys know some method/algorithm to do this verification with only 17 bytes max, thank you for all your help.
Generally you'd let the device establish a symmetric / secret key first, e.g. using ECDH and then use that secret key with a MAC algorithm to perform the message authentication. In that case 16 bytes / 128 bits is plenty.

For direct signatures, the BLS signature scheme is probably still the best out there, but for 128 bit level encryption - the lowest we commonly aim for - you'd still need a 384 bit signature.