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Re: [openpgp] AEAD Chunk Size

2019-03-28 19:10:55
On 3/28/19 at 4:47 PM, bartbutler=40protonmail(_dot_)com(_at_)dmarc(_dot_)ietf(_dot_)org (Bart Butler) wrote:

Maybe a reasonable compromise is, as we discussed a while ago, simply an upper bound on the chunk size rather than fixing it to a single value. What's a reasonable upper bound for constrained systems? 4MB?

The Arduino Uno, which the web site says is the most popular Arduino in the line <https://store.arduino.cc/usa/arduino-uno-rev3>, has:

 Flash Memory 32 KB (ATmega328P) of which 0.5 KB used by bootloader
 SRAM 2 KB (ATmega328P)
 EEPROM 1 KB (ATmega328P)

So it might be able to use a chunk up to 1KB without having to do the kind of pipelining that leads to security bugs and messy code.

YMMV!


In general, when asked about the smallest target for crypto algorithms, I think it was in the cryptography mailing list, the consensus was an 8 bit microprocessor with 64K of addressing would always be the target. People will always find a use for cheaper and smaller processors and 8 bits with 64K addresses seems to be where we have settled.

Cheers - Bill

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