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Re: [Dcrup] draft-ietf-dcrup-dkim-crypto-00

Scott Kitterman <sklist@kitterman.com> Fri, 19 May 2017 12:55 UTC

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Date: Fri, 19 May 2017 12:49:23 +0000
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From: Scott Kitterman <sklist@kitterman.com>
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Subject: Re: [Dcrup] draft-ietf-dcrup-dkim-crypto-00
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On May 19, 2017 7:51:47 AM EDT, "Mark D. Baushke" <mdb@juniper.net> wrote:
>Hi,
>
>I suggest that 2048 bit RSA be considered the minimum key size.
>Smaller sizes are not really safe these days.

2048 bit keys present operational problems in common DNS provisioning systems.  What advice should we offer those not currently able to publish a TXT record long enough for 2048?

I don't think the answer is don't bother with DKIM because it's pointless with a key < 2048.  Given the ephemeral nature of a DKIM signature's value, there's probably a combination of shorter keys and key rotation that's perfectly fine.

Scott K

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