[Cryptography] ratcheting DH strengths over time

[Albert Lunde]

On 11/15/2015 7:56 PM, Tony Arcieri wrote:
> On Sun, Nov 15, 2015 at 4:10 PM, ianG <iang at iang.org
> <mailto:iang at iang.org>> wrote:
>
>     How could we do this in a DH protocol?  I would suggest a schedule
>     over time.  Most or all of our implementations have a timebase
>     available. Something like this:
>
>     2015 - 1024
>     2016 - 1280
>     2017 - 1536
>     2018 - 1792

This isn't an unreasonable idea; at the same time views of "How 
breakable is algorithm X with strength Y" change over time.

The proposal to drop support for SHA1 in signatures 6 months sooner is 
this kind of decision; without there being an immediate attack on 
practical SHA1 signatures, the perception of risk has altered.