You are correct regarding key sizes of 1024 bits, but I was looking for the theoretical minimum key size rather than the practical minimum key size.
-----Original Message----- From: Wei Dai [mailto:[EMAIL PROTECTED] Sent: Thursday, April 08, 2004 4:39 AM To: [EMAIL PROTECTED] Subject: Re: Max Message Length When Signing? Yes, but why would you want to? You shouldn't use RSA keys less than 1024 bits long anyway because of insufficient security. On Wed, Apr 07, 2004 at 09:38:43PM -0700, David Brownell wrote: > 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
