[Cryptography] Dan Bernstein has a new blog entry on key breaking

Ray Dillinger bear at sonic.net
Sun Nov 22 16:48:44 EST 2015


Known plaintext is more common than you'd guess.

For example, the plugins for phbb that render user avatars produce
files (gif or png or jpg) in a standard format, size and color depth.
Those plugins, with their default settings of 256-color, 150x150-pixel,
gif get used across a lot of sites.  The pictures look different to
us, but the headers are identical when seen as data.

Each time a user avatar pic gets transmitted from any of those sites,
it's transmitted as its own packet and the first few blocks of the
payload will be identical because identical headers.

So, pick a block of that gif header as your known plaintext, and you'll
have millions of examples of it being used 'live' every day.

				Bear


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