Further BigInteger performance improvements

[Florian Weimer]

* Alan Eliasen:

> Florian Weimer wrote:
>> To provide some more background, most of us probably worry about
>> BigInteger performance in the 512 to 2048 bit range because that's the
>> range used for RSA cryptography (assuming that Java uses the Chinese
>> Reminder Theorem optimization for private key operations).
>
>    I understand the importance of this range in cryptography, and I
> especially understand the greater importance of the even smaller range
> that actually makes up the bulk of CPU time spent in cryptography, down
> in the 128-256 bit sizes.  Most practical crypto schemes tend to use
> those public-key algorithms with numbers of 512 to 4096 bits for the
> initial key exchange, but then use something like 256-bit AES for
> encrypting the actual data stream.

The symmetric algorithms relevant in practice (such as AES) don't do
arithmetic on big integers.

Your To: line was wildly wrong, I tried to correct that.