ChipWhisperer laughs at your AES-256 implementation. But it laughs with you, not at you.

The objective of ChipWhisperer is nothing short of revolutionizing the entire embedded security industry. Every designer who uses encryption in their design should be able to perform a side-channel attack, and understand the ramifications of these attacks on their designs. The open-source nature of the ChipWhisperer makes this possible, and my hope is that it becomes the start of a new era of hardware security research.

https://hackaday.io/project/956-chipwhisperer-security-research