RSA Encrypt: Key not valid for use in specified state.

[cjelec]

Hi,

I'm getting the dreaded "Key not valid for use in specified state." with the RSACryptoServiceProvider (vb.net 2008) when trying to encrypt a byte block of under 245 bytes using a public key loaded from an xml string.

I have searched everywhere for this, but the only answers I can find relate to the length of the data being encrypted which isn't the problem here because the length of the data I'm trying to encrypt is only 193 bytes.

I have checked the public key being used with the original key and they are exactly the same.

I would post my code but its dotted around quite a few classes. Its something like the following:

'Generate key
Dim xmlpublickey As String
Dim rsa As New RSACryptoServiceProvider

xmlpublickey = rsa.ToXmlString(False)

Then Later on, in the sending class

Dim xmlpublickey As String = getKey() 'this key does match exactly (also in length)
Dim rsa As New RSACryptoServiceProvider

rsa.FromXmlString(xmlpublickey)

Return rsa.Encrypt(data, False) 'Error here

Can anyone help?

Thanks loads in advance,

Chris

 

[cjelec]

I have done some tests and found that the encryption will only work if I use the private key (rsa.ToXmlString(True)) which defeats the object of using public/private key encryption...