On Sun, Jan 22, 2017 at 1:18 PM, Scott Kitterman <skl...@kitterman.com> wrote:
> No responsible operator has used the RFC minimum DKIM key sizes for a long > time. They were trivial to bypass half a decade ago. No one has ever > complained about 1024 bits default minimum being too big. I did once get a > complaint about the Debian opendkim package suggesting the minimum should > be 2048 bits. > As I recall there are issues using keys bigger than 1024 bits because construction and/or correct interpretation of TXT records that contain keys of that size or bigger has been problematic due to DNS provisioning software that does the former wrong and DKIM verifiers that do the latter wrong. To my knowledge, nobody has ever shown evidence that the larger keys are too computationally expensive to be used, or that any of the other things mentioned in Section 3.3.3 of RFC6376 are actually a problem. If we can nail those issues down, I think a lot of the practical resistance goes away, and ARC can easily say ">= 1024" or whatever we want and be done with it. -MSK
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