Speed of signing with RSACryptoServiceProvider

Question

I'm currently working on a simple piece of data signing. It's the first time I use signing so maybe I just do somehting wrong. But I don't think its normal that it takes 4.6 seconds to sign 448 bytes using a 512bit RSA and SHA1 hashing.

The code:

byte[] Data = enc.GetByte(MsgString); //Get Message as byte[]
//Data is 448 bytes long

RSACryptoServiceProvider Crypter = new RSACryptoServiceProvider(512);
Crypter.ImportCspBlob(Convert.FromBase64String(KeyString));

byte[] SignedData = Crypter.SignData(Data, "SHA1"); //Line takes 4.6 seconds

Why is this that slow? I found this : http://support.microsoft.com/kb/948080 , but thats a problem of .NET 2.0. I'm using 4.0.

Is it normal that this takes that long or is there an error?

Thanks for any help.

Answer 1

Just to let you know that I have been experiencing that same slowness getting SHA1 signed hashes. The some code that usually signed tens on hundreds of transactions per second, sudently, slowed down to 1 for every 5 seconds.

I was working at home and I was not connected to my company's network. After some googling, I have managed to spot the culprit. A bug the seems to afect RSACryptoServiceProvider on .Net Framework 2.0 - which I believe is EXACTLY the same code used on.Net Framework 4.0.

Since, according to http://support.microsoft.com/kb/948080, my temporary slowness may be due both RSACryptoServiceProvider's SignData or VerifyData methods trying to communicate to my companys's domain controller, I have decided to establish a VPN connection to my company, which was an imediate success.

Now I get SHA1 hashes again instantly, instead of waiting up to 5 seconds.

I know this is not a solution, but, at least, is a reasonable workaround. It also prevents us from loosing our sanity.