encrypt data in Javascript with "RSACryptoServiceProvider" Public Key -> Exceed Maximum Exception

Question

I have a Instance of the "RSACryptoServiceProvider" in my backend Code.

  oRsa = new System.Security.Cryptography.RSACryptoServiceProvider(2048);
  var Key = CryptoHelper.ExportPublicKey(oRsa);

the "key" is send to my Javascript Client wich uses JSEncrypt to encrypt the Data.

Problem now is I got the following error in my Backend: "The data to be decrypted exceeds the maximum for this modulus of 256 bytes."

Can System.Security.Cryptography.RSACryptoServiceProvider use a key size greater than 256? — ghangas, Dec 10 '15 at 11:50
A 2048 bit key can be used to encrypt a max of 245 bytes, if the encryption works presumably your length is less than this, how is the data received by the back end? as base64/hex string? Are you transforming this back into a byte[] correctly? — Alex K., Dec 10 '15 at 11:55
Does JSEncrypt.encrypt returen something base64 encoded? I thought these are the encrypted bytes? — Jochen Kühner, Dec 10 '15 at 12:55
I looked and yes it returns Base64 so you need to convert that to a byte array for decryption — Alex K., Dec 10 '15 at 13:49
So the question becomes to Jochen: did you decode the data before decrypting it? If not then Alex may have answered your question — Maarten Bodewes, Dec 10 '15 at 20:02
I now tried to use atob(xx) of the encrypted data, before I send it over the websocket! But I still get the same error on the backend! — Jochen Kühner, Dec 11 '15 at 07:20

score 1 · Accepted Answer · edited May 23 '17 at 11:52

1

edited May 23 '17 at 11:52

Community

answered Dec 11 '15 at 09:47

Jochen Kühner

1 Answers1