Re: [openpgp] AEAD Chunk Size

Bill Frantz <> Fri, 29 March 2019 04:40 UTC

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Date: Thu, 28 Mar 2019 21:39:54 -0700
From: Bill Frantz <>
To: Peter Gutmann <>, Bart Butler <>
cc:, Justus Winter <>, "Neal H. Walfield" <>, Jon Callas <>, Jon Callas <>
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Subject: Re: [openpgp] AEAD Chunk Size
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On 3/29/19 at 8:33 PM, (Peter Gutmann) wrote:

>Bill Frantz <> writes:
>>The Arduino Uno, which the web site says is the most popular Arduino in the
>><>, 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.
>And where does the PGP code and data memory itself fit in all this?

Well, we had a version of PGP running on an original IBM PC. 
With careful implementation, you might get the code into 32K 
program memory using the 2K R/W memory for buffers and working 
memory. You also might slip implementing all of the SHOULDs and 
perhaps some of the inappropriate MUSTs. You would probably have 
to also always make the tradeoff for space and not performance.

Remember, the original question was asked by an enbedded system 
developer. How small do they go? If they're looking at Raspberry 
Pi size machines, then they really have it comparatively easy.

Cheers - Bill

Bill Frantz        |"Insofar as the propositions of mathematics 
refer to
408-356-8506       | reality, they are not certain; and insofar 
they are | certain, they do not refer to reality.” 
-- Einstein