Too much data for RSA block fail. What is PKCS#7?

Question

Talking about javax.crypto.Cipher

I was trying to encrypt data using Cipher.getInstance("RSA/None/NoPadding", "BC") but I got the exception:

ArrayIndexOutOfBoundsException: too much data for RSA block

Looks like is something related to the "NoPadding", so, reading about padding, looks like CBC is the best approach to use here.

I found at google something about "RSA/CBC/PKCS#7", what is this "PKCS#7"? And why its not listed on sun's standard algorithm names?

Update:

I'm wondering, if is a padding problem, why this example run just fine?

import java.math.BigInteger;
import java.security.KeyFactory;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.RSAPrivateKeySpec;
import java.security.spec.RSAPublicKeySpec;

import javax.crypto.Cipher;

/**
 * Basic RSA example.
 */
public class BaseRSAExample
{
    public static void main(
        String[]    args)
        throws Exception
    {
        byte[]           input = new byte[] { (byte)0xbe, (byte)0xef };
        Cipher          cipher = Cipher.getInstance("RSA/None/NoPadding", "BC");
        KeyFactory       keyFactory = KeyFactory.getInstance("RSA", "BC");

        // create the keys

        RSAPublicKeySpec pubKeySpec = new RSAPublicKeySpec(
                new BigInteger("d46f473a2d746537de2056ae3092c451", 16),
                new BigInteger("11", 16));
        RSAPrivateKeySpec privKeySpec = new RSAPrivateKeySpec(
                new BigInteger("d46f473a2d746537de2056ae3092c451", 16),  
                new BigInteger("57791d5430d593164082036ad8b29fb1", 16));

        RSAPublicKey pubKey = (RSAPublicKey)keyFactory.generatePublic(pubKeySpec);
        RSAPrivateKey privKey = (RSAPrivateKey)keyFactory.generatePrivate(privKeySpec);

        // encryption step

        cipher.init(Cipher.ENCRYPT_MODE, pubKey);

        byte[] cipherText = cipher.doFinal(input);

        // decryption step

        cipher.init(Cipher.DECRYPT_MODE, privKey);

        byte[] plainText = cipher.doFinal(cipherText);

    }
}

Update 2:

I realized that even if I use just Cipher.getInstance("RSA", "BC") it throws the same exception.

Answer 1

RSA can only be used to encrypt, when the number of bits being used to encrypt is greater then the size of the thing you are tying to encrypt + 11 bytes

Public-Key Cryptography Standards - PKCS