File encryption using java

Since the output file consists of the encrypted AES key, the initialization vector and the byte signature at the end, the length of the encrypted message is:. Note that this length may be different from the length of the unencrypted message since encryption proceeds by blocks.

This assures B that A has indeed sent the message. The static method authFile is shown below. It decrypts the message update dataLen and verifies the signature of the decrypted message. In this article, we saw how to encrypt a file for a receiver and also sign it so the receiver is sure it came from us. Great article, but why 6. So private or public? Or i missfallowed something? Your email address will not be published. Notify me of follow-up comments by email. Notify me of new posts by email.

This method then serves as a method of secure file exchange with Alice. In the following examples, we demonstrate using the private key for encryption. To go the other way, you can replace the private key with the public key. The main class handling the encryption is the Cipher class. We create a suitable cipher, initialize it with the private key or the public key as required, see above , and perform the encryption.

Once we obtain the file encrypted with the private key, we can decrypt it using the public key. The process is similar and shown below.

We write the decrypted data to an output file for verification called verFile below. Let us now run a couple of tests to check that the encryption and decryption proceeded correctly. We use the following simple test file:. Let us now try a larger file, about kb in size. However, on encryption, we encounter the following error:. Well, it so happens that asymmetric encryption has good performance only for small sizes. We cover this in the next part of the article. Here is the source code referenced in this blog post.

Your email address will not be published. Notify me of follow-up comments by email. This is an AES encryption program, so why does it save the text to a. Since Peter says:. Nav says:. Anonymous says:. Dragan Bjedov says:. Narendra says:. Grace says:. Yohannes M Alemu says:. Michael Kangethe says:. Robin says:.