Actually, I spent more time working with the library, and found that keys < 361 bits are not able to sign messages. I found this value by generating a key of N bits, and then attempting to sign a 1 byte message using that key. All key sizes failed < 361. Is there a way I could have computed this value programmatically rather than through trial and error?
Thanks! -----Original Message----- From: Wei Dai [mailto:[EMAIL PROTECTED] Sent: Wednesday, April 07, 2004 8:09 PM To: [EMAIL PROTECTED] Subject: Re: Max Message Length When Signing? When you use RSASS, you should be able to sign arbitrarily long messages, as long as the key size is sufficient to handle the hash size (which is fixed for all message lengths). If, using the same key, you're able to sign short messages but not long ones, then something is wrong. Please post sample code if that's the case. On Wed, Apr 07, 2004 at 08:51:54AM -0700, David Brownell wrote: > I am attempting to sign a message using the test application that > ships with the Crypto++ library (which uses RSASS to sign a message). > If I use a very small key to sign a very large file, I get a > KeyTooSmall exception. I know that in the real world hashes of > messages are signed rather than the messages themselves to alleviate > this problem, but for the sake of argument, is there a way to tell at > run time that maximum message size that can be signed for a given private key? > > Thanks in advance for your help! > David Brownell
