Encrypting a big file
I hace a database created, whit administrator program createthe file with all products, are 6000 products, this file must be shared to others client-programs, that i want is that my administrator program upload to a server and with the client-program download it, but nobody can open the dile to view the information. i want the file will be safe. I recomend me encrypting with RSA, but i dont have clear this process for a file. I have understood that the size is multiplied. What do you recommend for encrypting the file and a example for this.
I'm not sure what you want to do.
RSA must not be used for encrypting regular data, it makes it unsafe.
For big data RSA is slow as well as unsafe.
RSA (or alike) should be used for symmetric key exchange.
BE aware of time attacks in RSA key exchange process.
RSA should be included in Java's cryptography package.
For encrypting files you may want to use a block cipher (those are usually best) found I Java's cryptography package. You can (but should not) also go old school and use a simple Vigenère cipher.