Re: Max Message Length When Signing?

[Webmaster]

I ran into the same exact problem.  I was puzzled, because I am using 
functions very similar to the ones in the test app, and it allows a 
message length of 1024.  And I was getting it to abort with around 180 
chars.  Is there some documentation on the ratio of key length to 
message length?

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