Have you a public key certificate?

If you do, provide it to a friend who can import it into an e-mail client
like outlook, outlook express, mozilla, thunderbird. When sending you
e-mail, have him use that certificate to encrypt mail to you.
Import your private key into your e-mail program and specify that key as the
decryption/signing key.
Your e-mail program will do the work of decryption.

Alternatively, get pgp encryption/decryption and import your keys into it.

Incidentally, you can get freemail certificates and private key from Thawte
(www.thawte.com) [ look for freemail] for free.
Ed

Hi What you need is an Certificate for your
public key. And than do someting like this
to initialize your Cipher.

X509Certificate cert = ...
Cipher rsaCipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
rsaCipher.init(Cipher.ENCRYPT_MODE, cert);

With that Cipher you can create an CipherIn- or OutputStream.

At the Decryption site of your application you can
initilize your Cihper with the Private-Key.

You should store the private key in an password encrypted
Keystore (ex. JDKPKCS12KeyStore from BouncyCastle)

Hope it helps

But you should think about symetric encryption.
Create a symetric key, encrypt message with "symkey" and
encrypt the "symkey" with the public key and send both
encrypted message and encrypted "symkey".
On the other side decrypt "symkey" and with that decrypted
"symkey" decrypt the message.

If you must ensure that the message comes from the server
you should sign something: either the symkey before encryption
or the complete messagebundle(encrypted message,encrypted key).

Hope it helps even though my bad english

Kind regards.
Sebastian