RSA 1024 ridiculous

Roscoe eocsor at
Sun Jun 17 20:43:31 CEST 2007

RSA keysize will influence how long it takes you to encrypt or sign a
message. But how long the RSA signing/encryption step takes is going
to be the same no matter what the message length. That's because you
are only ever signing a hash of the message or encrypting the
symmetric session key used to encrypt the message.

I doubt I could notice the difference on my computer between
encrypting at 20GB tarball with a 1024bit key or a 4096bit key. With
large amounts of data most of the time is spent on the symmetric
encryption (or perhaps on compression or disk io?). The bigger the
amount of data you're encrypting the less you're going to notice RSA
keysize differences :).

On 6/18/07, Andrew Berg <bahamut at> wrote:
> Hash: RIPEMD160
> Robert Hübener wrote:
> > Andrew Berg wrote:
> >> Try signing/encrypting files that are tens, hundreds, or
> >> thousands of megabytes in size. Sure, your average machine can
> >> sign/encrypt messages that don't even fill a cluster without
> >> breaking a sweat, but if the sensitive data is large, RSA-4096
> >> isn't a good choice unless a gov't agency wants that data.
> > The work for the RSA-part of the algorithm is always the same: It
> > only has to process either the hash of the message/file or the key
> > for the symmetric cipher.
> I don't completely understand. Does this mean that
> encryption/signature time is only dependent on the hash, and that RSA
> key size doesn't matter in this regard?
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