Key sizes, public vs. secret key

Justin Troutman
Mon Jun 10 21:59:01 2002

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Subject: Key sizes, public vs. secret key

> Then I wonder, due to that fact, does it mean that if I make a secret key
that >has e.g. 8192b size, that the messages are no stronger protected than
if I had >used 1024b secret key?

Well, assuming you are talking symmetrics, it is apparent that the larger
the key, the stronger, initially, however, if you are comparing the
relations of a 8192-bit symmetric key vs. a 1024-bit asymmetric, the
symmetric is evidently stronger, by far.

To make a comparison of symmetric/asymmetric key sizes, you could compare a
1024-bit asymmetric key (public key) to an 80-bit symmetric key.  Since the
levels of performance and attack properties are different between the two,
it is not accurate to compare any other key sizes between the two in this

If I had to recommend key sizes based on security, performance, and speed,
I'd say:

Symmetric: 128 bits (You'll find this as fast as a 64-bit key)
Asymmetric: 2048 bits

Hope this helps.


Justin T.