> when I encrypt the message, message should be
> BigInteger.That BigInteger will be encrypted by RSA.
I think you have a fundamental misunderstanding of the encryption process (no problem; everyone must begin somewhere). You should start by reading the following:
[url=http://java.sun.com/developer/technicalArticles/Security/JCE/]Java 2 Cryptography Extension: Encrypting and Decrypting Data[/url]
[url=http://java.sun.com/docs/books/tutorial/security1.2/]Security in Java 2 SDK 1.2[/url]
[url=http://builder.com.com/5100-6370-1046088.html]Master the basics of Java Cryptography Extension (JCE)[/url]
[url=http://www-128.ibm.com/developerworks/java/jdk/security/142/]IBM 1.4.2 developer kit: Security information[/url]