Re: Should Ada runtime provide special primitives for cryptography?

[Dennis Lee Bieber <wlfraed@ix.netcom.com>]

On Wed, 1 Oct 2014 08:42:17 +0000 (UTC), Natasha Kerensikova
<lithiumcat@instinctive.eu> declaimed the following:

>However, when actually implementing cryptographic stuff, cleverness from
>compiler and optimizer are often enemies. For example, overwriting a
>buffer with zeroes might be optimized out when the buffer is not
>accessed again.
>
	Cryptographic "zeroing" does not fill a buffer with 0x00 values. One
approved method is to:

generate random sequence (in a second buffer as you'll need it again)
copy random sequence into crypto buffer
compare buffers to ensure data was changed
invert the bits of the random sequence
copy random sequence into crypto buffer
compare to ensure all data changed
generate second random sequence
copy second sequence into buffer
compare buffers

The first two copy operations ensure every bit in the buffer has been
toggled to both states -- the compares ensure you don't have a "sticky
bit".
-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
    wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/