I did investigate this and there is a valid reason for this. There are DNS service providers that limit TXT records to a single 255 character string (even though DNS has no such limit). 2048 bit key records won't fit.
DKIM is designed to give some minimal level of assurance the message hasn't been modified, as such, it's not likely to be a primary target of someone seeking to factor 1024 bit keys (the same is not true of smaller keys which were successfully factored in the wild a few years ago). The generally recommended best practice for DKIM keys is to rotate them regularly to mitigate risks like this. Scott K On Sat, 14 Jun 2014 11:42:44 +0200 Kurt Roeckx <k...@roeckx.be> wrote: > Package: opendkim > Version: 2.9.2-1 > Severity: important > > Hi, > > It seems that the default MinimumKeyBits is still set to 1024. > Please change that to 2048. All certificates for server > authentication (what DKIM does) with RSA keys smaller than 2048 > should either have expired before 2014 or should have been > revoked. There is no excuse for using RSA keys smaller than 2048 > bit. > > > Kurt > > >
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