Translating C# RSACryptoServiceProvider into JAVA Code

Question

I was given this C# code written by the web service team that exposes some web service that I\'m planning to consume. My password needs to be encrypted with this code so tha

Answer 1

According to MSDN docs on RSACryptoServiceProvider.Encrypt, when the second argument is false the cipher uses PKCS#1 v1.5 padding. So right off the bat your cipher spec is incorrect.

Try RSA/ECB/PKCS1PADDING instead.

You are converting your key material to much in your second code example and you corrupted it which ends up making your cipher think you have more key material than you actually have and makes your message too long (which is triggering your error) as well as unintelligible to the decryption cipher on the other end. Convert directly to byte arrays and pass those to BigInteger.

String modulusString = "...";
String publicExponentString = "...";

byte[] mod = Base64.decodeBase64(modulusString);
byte[] e = Base64.decodeBase64(publicExponentString);

BigInteger modulus = new BigInteger(1, mod);
BigInteger publicExponent = new BigInteger(1, e);