On 09-07-2010 03:31, Chuck Pareto wrote:
My group is using RSA with a key thats 2048 in size. We want to encrypt
strings that are longer then this key size gives.
If we switch to a key that is 4096 what is the max string length we can
encrypt? is it double?
You normally don't encrypt data directly with RSA. You use RSA to
encrypt a random encryption key (such as a 256 bit AES key), using a
standardized format (such as PKCS#1v2.0) to turn the random key into
a value which can be safely encrypted with RSA without making that RSA
key easier to break.
Then you encrypt your data (up to whatever limit is safe for the
chosen symmetric encryption algorithm, such as 256 bit AES with
mode=GCM).
I think you should go back and read some of the fundamental teachbooks
on crypto before trying such things.
The two most commonly recommended books are
"Handbook of Applied Cryptography" ("HAC")
"Applied Cryptography, 2nd edition" ("AE2") by Bruce Schneier
Both books are somewhat old on what algorithm names and sizes they
mention or recommend, but the principles stated in those books are
still valid and worth knowing.
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