From the datasheet, I see that there is a Bitscrambler peripheral that seems to be very similar in flexibility to the Raspberry Pi Pico's PIO:
> Since bitwise operations can be relatively CPU-intensive and DMA is designed specifically to offload such work from the CPU, ESP32-S31 integrates two dedicated peripherals called BitScramblers. These modules are designed to transform data formats during transfers between memory and peripherals. One BitScrambler handles memory-to-peripheral (or memory-to-memory) transfers, while the other is dedicated to peripheral-to-memory transfers. While BitScramblers can handle the bitwise operations mentioned earlier, they are in fact flexible, programmable state machines capable of performing more advanced transformations as well.
Here's hoping that it's as useful as the Pi Pico's PIO
In my opinion, the author understates how good AES-GCM-SIV is:
> The solution they designed is described in that linked paper: AES-GCM-SIV, which is able to tolerate some number of nonce collisions, but under a weaker notion of security that is only really applicable to that use-case (where the data being encrypted is itself random).
AES-GCM breaks catastrophically if you reuse a nonce; but the only thing that happens if you reuse a nonce with AES-GCM-SIV for two messages is that an attacker can see if the messages are equal (since AES-GCM-SIV is a deterministic algorithm, this is pretty much unavoidable). So yes, "weaker notion of security", but still applicable to a lot more than just that use-case. I wonder why AES-GCM-SIV is not used more, since it's so developer-friendly and misuse resistant.
> Since bitwise operations can be relatively CPU-intensive and DMA is designed specifically to offload such work from the CPU, ESP32-S31 integrates two dedicated peripherals called BitScramblers. These modules are designed to transform data formats during transfers between memory and peripherals. One BitScrambler handles memory-to-peripheral (or memory-to-memory) transfers, while the other is dedicated to peripheral-to-memory transfers. While BitScramblers can handle the bitwise operations mentioned earlier, they are in fact flexible, programmable state machines capable of performing more advanced transformations as well.
Here's hoping that it's as useful as the Pi Pico's PIO