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RSA Cipher

John Carr
Greenhorn

Joined: Jan 16, 2010
Posts: 17
I want to pass messages to and from the server/client and use a RSA cipher, but I can't figure out how to generate a pair, and pass the public key to the other, and then use it.

I am trying to modify this code that I found via Google:
Ulf Dittmer
Marshal

Joined: Mar 22, 2005
Posts: 42277
    
  64
The code already generates a key pair, and extracts both private and public key, no? The data to be used can be gotten from either key by calling the "getEncoded" method.


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John Carr
Greenhorn

Joined: Jan 16, 2010
Posts: 17
I know, but I want to specifically set a public key that coincides with the private key the server generates.

I can't figure out how to set a key...
Ulf Dittmer
Marshal

Joined: Mar 22, 2005
Posts: 42277
    
  64
Once you have the bytes that make up a key, you can create a Key object from it like this:
John Carr
Greenhorn

Joined: Jan 16, 2010
Posts: 17
Well Ulf, I tried fiddling with it for a bit, and googling the error, and I can't seem to get it...

Here is what I have atm:


And here is the error:
Exception in thread "main" java.security.InvalidKeyException: Neither a public nor a private key
at sun.security.rsa.RSAKeyFactory.engineTranslateKey(RSAKeyFactory.java:193)
at sun.security.rsa.RSAKeyFactory.toRSAKey(RSAKeyFactory.java:111)
at com.sun.crypto.provider.RSACipher.init(RSACipher.java:260)
at com.sun.crypto.provider.RSACipher.engineInit(RSACipher.java:205)
at javax.crypto.Cipher.init(Cipher.java:986)
at javax.crypto.Cipher.init(Cipher.java:935)
at TestRsa2.encrypt(TestRsa2.java:32)
at TestRsa2.main(TestRsa2.java:70)
greg stark
Ranch Hand

Joined: Aug 10, 2006
Posts: 220
Ulf Dittmer wrote:Once you have the bytes that make up a key, you can create a Key object from it like this:


That is for a secret (symmetric) key. For a public key, you create an X509EncodedKeySpec from the result of PublicKey.getEncoded(). You supply the X509EncodedKeySpec instance to a KeyFactory instance. Using the getInstance() method to get an RSA instance. Then use the generatePublic() method and supply the X509EncodedKeySpec to it to get the public key.


Nice to meet you.
John Carr
Greenhorn

Joined: Jan 16, 2010
Posts: 17
Thanks Greg, I finally got it to work.
 
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subject: RSA Cipher