java RSA Multiple Encryption

Question

I encrypt my message with a symmetric key and the symmetric key itself has to be further encrypted with different RSA public keys. When I tried to implement the above I got the following error:

javax.crypto.IllegalBlockSizeException: The input was invalid: Invalid input length.
        at com.rsa.shareCrypto.j.hD.engineDoFinal(Unknown Source)
        at javax.crypto.Cipher.doFinal(Cipher.java:2087)
        at wrap1.main(wrap1.java:69)

Is there a way to solve this problem ?

i need to do something like this [[[[key]PK-A]PK-B]PK-C], where PK-A = Public key of A, similarly PK-B and PK-C.

Below are the codes that i tried here are the codes

String InitialKey = "2011BCSChampionA";

byte[] initkey = InitialKey.getBytes();
// First level encryption of the key

KeyPairGenerator keyGen = KeyPairGenerator.getInstance("RSA");

keyGen.initialize(1024);
KeyPair keypair = keyGen.genKeyPair();
PrivateKey privateKey = keypair.getPrivate();
PublicKey publicKey = keypair.getPublic();
Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.ENCRYPT_MODE, publicKey);
byte[] cipherData = cipher.doFinal(initkey);
// Second level of encryption
KeyPairGenerator keyGen1 = KeyPairGenerator.getInstance("RSA");
keyGen1.initialize(1024);
KeyPair keypair1 = keyGen1.genKeyPair();
PrivateKey prvKey = keypair1.getPrivate();
PublicKey pubKey = keypair1.getPublic();
Cipher cipher1 = Cipher.getInstance("RSA");
cipher1.init(Cipher.ENCRYPT_MODE, pubKey);
byte[] cipherData_new = cipher1.doFinal(cipherData);

Is there a way to solve this problem ? If you post your code too, most definitely yes! — ppeterka
– ppeterka, Commented Oct 21, 2012 at 20:39
Does your encryption algorithm require block length that are mod 8? I seem to remember this about java... — daniel gratzer
– daniel gratzer, Commented Oct 21, 2012 at 20:40

Serge · Accepted Answer · 2012-10-22 21:17:04Z

2

Either you should pad your data to satisfy the encryption algorithm requirements or you should create the instance of Cipher class pointing the padding to use, e.g.:

cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");

As you need to use asymmetric keys then initialize your cipher the following way:

cipher = Cipher.getInstance("RSA/ECB/PKCS5Padding");

edited Oct 22, 2012 at 21:17

answered Oct 21, 2012 at 20:45

Serge

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2 Comments

user1763730 Over a year ago

i have to use asymmetric algorithm like RSA. Its kind of similar to Onion protocol.

user1763730 Over a year ago

i suppose its PKCS1Padding. i tried cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding"); i still get the following error javax.crypto.IllegalBlockSizeException: The input was invalid: Invalid input length. i need to do something like this [[[[key]PK-A]PK-B]PK-C] where PK-A = public key of A, similarly PK-B, PK-C i do this layered encryption and then i decrypt from the outer wall.

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