On Mon, Nov 10, 2014 at 5:59 PM, Nikos Mavrogiannopoulos <[email protected]> wrote:
> On Mon, 2014-11-10 at 11:48 -1000, Daniel Kahn Gillmor wrote: > > > After some debugging it turns out that the failing criteria is that > > > multiple of 64 bits requirement[1]. For some reason I've gotten a 1023 > > > bit prime, even though I called gnutls_dh_params_generate2() with 1024 > > > as the argument. > > ugh. Java is at fault here -- there's no sense in this particular > > severe limitation. if they're willing to use 512-bit DHE parameters and > > 1024-bit DHE parameters, they should be willing to use 1023-bit DHE > > parameters. > > That's indeed quite some arbitrary limitation. > I think that the actual limitation in question is that Java is requiring the prime length to be a multiple of 64. Presumably this dates back to FIPS-186-1 which did require prime lengths to be multiples of 64. The limitation on the prime length is supposedly being relaxed in Java 8. > > That said, i suppose it's possible that gnutls could always ensure that > > the high bit is set when generating a prime of a given size. > > That should be the case in gnutls 3.3.x. That version delegates to > nettle the DH parameter generation and nettle seems to be more precise. Thanks, I'll try that. -brian
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