Java Aes 128 Key Generator
Sep 04, 2018 AES supports key lengths of 128, 192 and 256 bit. AES comprises of 3 block ciphers AES-128, AES-192 and AES-256, each cipher encrypts and decrypts the data in the block of 128 bits using the secret key of 128, 192 and 256 bits respectively.
“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
- Encryption Key Generator. The all-in-one ultimate online toolbox that generates all kind of keys! 64-bit 128-bit 256-bit 512-bit 1024-bit 2048-bit 4096-bit.
- The Java KeyGenerator class (javax.crypto.KeyGenerator) is used to generate symmetric encryption keys.A symmetric encryption key is a key that is used for both encryption and decryption of data, by a symmetric encryption algorithm. In this Java KeyGenerator tutorial I will show you how to generate symmetric encryption keys.
- 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.
- Conclusion
1. Introduction
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:
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:
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.
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.
“The secret of education lies in respecting the pupil.”
― Ralph Waldo Emerson
Contents
- Conclusion
1. Introduction
In the previous part of this article, we covered the use of RSA for file encryption and decryption in java. Using RSA directly for file encryption will not work since it can only be used with small buffer sizes. In our particular case, with an RSA key size of 2048 bits, we ran into a limitation of a maximum of 245 bytes for the data size.
The solution for this limitation is to use a symmetric algorithm such as AES for encryption while using RSA for encrypting the AES secret key itself. When using AES for encryption, the initialization vector (IV) also needs to be communicated to the receiver for being able to decrypt the message. The entire process of using AES for encryption is covered in detail in this article here.
In the current case, we will generate an AES key, use the AES key for encrypting the file, and use RSA for encrypting the AES key. The output file is generated by including the encrypted AES key at the beginning of the file, followed by the initialization vector (IV) and finally the file data encrypted by AES. This way, just the output file can be delivered to the receiver, instead of the three separate components.
[Note: Check out how to use AES for file encryption and decryption in python.]
2. Java Imports
These are the required java imports for the implementation
3. Generating the AES Key
First step is to generate the AES key which will be used for the encryption. We generate a key of size 128 bits.
Free office 2010 cd-key. We also need the initialization vector of the same size as the key, which we generate as follows (along with the required IvParameterSpec):
4. Loading the RSA Private Key
Load the RSA private key from file using the appropriate class.
5. Save the AES Key
As mentioned above, the first part of the output file contains the encrypted AES key. For encryption, we use the Cipher class with the RSA private key and save it as follows:
6. Write the Initialization Vector
The initialization vector is next written to the output file. This is required for decryption using the AES key.
7. Encrypting the File Contents using the AES Key
The final step is to encrypt the contents of the file using the AES and write it to the output file.
Close the output file and send it to the receiver.
8. Decrypting the File using the RSA Public Key
Since the private key has been used for encryption, the public key can be used for decrypting the file contents. Remember that the file includes the AES key encrypted with the RSA private key at the beginning followed by the initialization vector, and the encrypted file data itself. So the decryption process has to handle all these steps in order to get at the file data.
9. Load the RSA Public Key from File
We use the following code to load the RSA public key from a file where it has been saved in binary format.
10. Load the AES Secret Key
Open the encrypted file and load the AES secret key. The AES secret key can be obtained from this data by decrypting using the RSA public key.
11. Read the Initialization Vector
Next in the file is the initialization vector. Load it as follows:
12. Decrypt the File Contents
Now comes the actual decryption of the file contents using the AES secret key. The output is written into a file with the extension .ver for verification purposes.
The static method processFile() is defined as before.
At this point the whole file has been decrypted and saved. You can verify that it matches the original file contents.
Conclusion
File encryption and decryption using RSA is somewhat involved since RSA encryption has a very low limit on the data that can be encrypted. The previous part of the article covered the details. To encrypt larger quantities of data, we need to use a symmetric algorithm such as AES for encryption and RSA for encrypting the AES key itself.
Java Aes 128 Key Generator Reviews
And here is the source code relevant to this blog post.