- So I wish to encrypt a string using AES-256 and want to provide the user to specify the password for unlocking the string. I plan to use sha-256 to hash to users entered password and use this as the key. Deriving 256-bit key from PBKDF2-SHA1. Using an AES-256-GCM key as a salt to SHA-256. Hot Network Questions.
- The AES key is nothing more than a specific sized byte array (256-bit for AES 256 or 32 bytes) that is generated by the keytool (see above).
- How to generate 256 bits AES key duplicate. For generating AES key of 256 bits, i wrote following code. Java 256-bit AES Password-Based Encryption.
- Oct 30, 2017 The process for encrypting and decrypting using AES is a bit involved. First you generate an IV (initialization vector) and then generate (or load) a secret key. Next you create a cipher object which you can use for encryption and decryption.
“There’s as many atoms in a single molecule of your DNA as there are stars in the typical galaxy. We are, each of us, a little universe.” ― Neil deGrasse Tyson, Cosmos
Contents
- Conclusion
1. Introduction
This is the first time I've written a class in Java to do encryption using AES. Since security is involved I would love it if someone could take a look at it and let me.
The Advanced Encryption Standard (AES) is a standard for encryption and decryption that has been approved by the U.S. NIST (National Institute of Standards and Technology) in 2001. It is more secure than the previous encryption standard DES(Data Encryption Standard) and 3DES(Triple-DES). You should be using AES for all symmetric encryption needs in preference to DES and 3DES (which are now deprecated).
Symmetric Encryption refers to algorithms that use the same key for encryption as well as decryption. As such, the key should be kept secret and must be exchanged between the encryptor and decryptor using a secure channel.
The core java libraries provide good support for all aspects of encryption and decryption using AES so no external libraries are required. In this article, we show you how to properly perform encryption and decryption using AES with just the core java API.
[Note: Check out how to use AES for file encryption and decryption in python.]
2. The Imports
We need the following import statements for the program.
3. Generate an Initialization Vector (IV)
When using AES with a mode known as CBC (Cipher Block Chaining), you need to generate an initialization vector (IV). In the CBC mode, each plaintext block is XORed with the previous ciphertext block before being encrypted. So you need an initialization vector for the first block. To produce different ciphertext with each run of the encryption (even with the same plaintext and key), we use a random initialization vector.
To generate the IV, we use the SecureRandomclass. The block size required depends on the AES encryption block size. For the default block size of 128 bits, we need an initialization vector of 16 bytes.
From the initialization vector, we create an IvParameterSpecwhich is required when creating the Cipher.
You can save the initialization vector for transmission along with the ciphertext as follows. This file can be transmitted plainly i.e. no encryption is required.
4. Generating or Loading a Secret Key
If you do not already have a key, you should generate one as follows:
If you have a key (maybe one generated previously and stored securely), you can load it from a binary key file using the following code:
If you need to save a generated key for future usage (maybe for loading using the above code), you can do it as follows:
5. Creating the Cipher
The Cipher object is the one that handles the actual encryption and decryption. It needs the secret key and the IvParameterSpec created above.
When encrypting, create the Cipher object as follows:
For decryption, you need to load the initialization vector and create the IvParameterSpec.
Now you can create the Cipher object:
6. Encrypting a String
Once the Cipher object is created, you can perform the encryption. The encryption process works with byte arrays.
To encrypt a String, first convert it to a byte array by encoding it in UTF-8. Then write the data to a file as follows:
7. Decrypting Back to a String
Read back encrypted text and convert it to a String as follows:
Generate 256 Bit Aes Key Java Download
8. Encrypting a File
The procedure for encrypting a file is a bit more involved. Read the input data in a loop and invoke Cipher.update(). If a byte array is returned, you can write it to the output file. Finally wrap up with a Cipher.doFinal().
Invoke the encryption as follows:
Generate 256 Bit Aes Key
9. Decrypting a File
The outfile obtained from the above procedure can be decrypted quite simply by specifying the decrypt mode as follows:
And that covers the whole story of encryption and decryption using AES.
Generate 256 Bit Aes Key Java Key
Conclusion
The process for encrypting and decrypting using AES is a bit involved. First you generate an IV (initialization vector) and then generate (or load) a secret key. Next you create a cipher object which you can use for encryption and decryption.