Aes implementation in java

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A NIST compliant implementation of the AES (Rijndael) cipher in Java.

NWc0de/AES

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README.md

This repository is home to an implementation of the AES (Rijndael) cipher in Java. The suite of methods and ultimate cipher functions were tested with example vectors provided by NIST FISP-197 and NIST SP 800-38A to prove compliance with NIST specification (CipherTests.java and CounterModeTests.java).

java AES -k keyfile> -o output file> -f input file> -v IV file> -d optional: decryption> -CTR optional: counter mode>

An Initialization Vector is required to run the program because the default mode is CBC (Cipher Block Chaining). 16 byte IVs can be generated with

dd if=/dev/urandom of=initvector bs=4 count=4

Any mode of generation is acceptable for ICBs however the ICB should be unique for each message/file. A single ICB can be used for up to 2^m blocks of plaintext, where m is the number of bits used to form an integer in the standard incrementation function. In this implementation m=32 so a new ICB must be generated for every 64 gigabytes of plaintext that is processed.

Note: In CTR mode the IV corresponds to the initial counter block (ICB).

In CBC mode the initialization vector (IV) does not need to be secret. It may be transmitted in plaintext along with the ciphertext. However, the IV must be unique across invocations of the cipher (ie. for each file/message that is encrypted, a unique, unpredictable IV should be generated.) This process should use a secure random number generator to produce IVs.

More information about ICBs, IVs, and AES modes can be found in NIST SP 800-38A.

Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.

Please make sure to update tests as appropriate.

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An implementation of the AES algorythm in java

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TheDome/Java-AES-implementation

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README.md

This is a little Project, I had. This here is a simple implementation of the AES Algorythm based on the one from Rijndael. At the moment, it can de- and encrypt files.

If you only want to encrypt:
[name] inputfile
Then the key will be stored as inputfile.aeskey and the outputfile will be stored as inputfile.enc

For encryption with a specific key
[name] -i inputfile -k keyfile -e
Then the output will be stored as inputfile.enc

For the decryption
[name] -i inputfile -k keyfile -d
Here the file to output will be stored (as not other mentioned) as inputfile minus the last 4 characters (default without .enc)

-i inputfile File for input -h Display the help -o output File for output -k keyfile File of the key -v [optional] mode Enable the verbose mode -p Enable the percentag mode to display the percent finished (May spam some command promts) -e or -d Encryption or decryption mode -p Enable the percentage mode to display percent (Slows down encryption) 

About

An implementation of the AES algorythm in java

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AES Implementation In Java with ECB | CBC | OFB | CFB Modes Of Operation

Output
dhanoopbhaskar@dhanoop-laptop:~/workspace/Copy/crypto/run_aes$ java AESkeygen
Key generated and saved in AESkey.txt
dhanoopbhaskar@dhanoop-laptop:~/workspace/Copy/crypto/run_aes$ java AESencrypt
Usage: java < classname > < mode >
< mode >:= (ECB|CBC|OFB|CFB)
dhanoopbhaskar@dhanoop-laptop:~/workspace/Copy/crypto/run_aes$ java AESencrypt ecb
Encryption done! Please check AESciphertext.txt for output!
dhanoopbhaskar@dhanoop-laptop:~/workspace/Copy/crypto/run_aes$ java AESdecrypt ecb
Decryption done! Please check AESplaintext.txt for output!
dhanoopbhaskar@dhanoop-laptop:~/workspace/Copy/crypto/run_aes$ java AESencrypt cbc
Encryption done! Please check AESciphertext.txt for output!
dhanoopbhaskar@dhanoop-laptop:~/workspace/Copy/crypto/run_aes$ java AESdecrypt cbc
Decryption done! Please check AESplaintext.txt for output!
dhanoopbhaskar@dhanoop-laptop:~/workspace/Copy/crypto/run_aes$ java AESencrypt ofb
Encryption done! Please check AESciphertext.txt for output!
dhanoopbhaskar@dhanoop-laptop:~/workspace/Copy/crypto/run_aes$ java AESdecrypt ofb
Decryption done! Please check AESplaintext.txt for output!
dhanoopbhaskar@dhanoop-laptop:~/workspace/Copy/crypto/run_aes$ java AESencrypt cfb
Encryption done! Please check AESciphertext.txt for output!
dhanoopbhaskar@dhanoop-laptop:~/workspace/Copy/crypto/run_aes$ java AESdecrypt cfb
Decryption done! Please check AESplaintext.txt for output!
dhanoopbhaskar@dhanoop-laptop:~/workspace/Copy/crypto/run_aes$

About Input/Output Files
AESkeygen.java — (output) AESkey.txt
AESencrypt.java — (input) AESkey.txt & AESplaintext.txt (output) AESciphertext.txt
AESdecrypt.java — (input) AESkey.txt & AESciphertext.txt (output) AESplaintext.txt

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Java AES Encryption Decryption Example

AES stands for advanced encryption standard and is the most commonly used symmetric algorithm to encrypt sensitive data and can be used in both software and hardware.

The AES algorithm is symmetric, meaning that it uses only one key for encryption and decryption, and due to this reason, the key must be shared between the sender and the receiver.

The standard has three key sizes, which include 128 , 192 , and 256 and each of the ciphers encrypts and decrypts data in blocks of 128 bits.

The key sizes perform 10 , 12 , and 14 rounds on the data for 128 , 192 , and 256 respectively, making 256 the stronger algorithm among them.

By default, the java implementation of the AES algorithm uses 128 key size, and in this tutorial, we will implement the algorithm to encrypt and decrypt a message.

Generate a shared key

To generate a key that will be used for both encryption and decryption of our message, we will use the getInstance() method of the KeyGenerator class in java and pass string AES to the method.

The getInstance() method throws a NoSuchAlgorithmException if no provider supports a KeyGeneratorSpi of the specified algorithm and a NullPointerException if the algorithm provided is null .

The KeyGenerator will create an instance of the AES algorithm that we will use to generate a key using the generateKey() method of the class.

This class generates a symmetric secret key, and once a key has been generated, the same object can be used to create other keys.

Use the encodeToString() method of Base64.Encoder to view the generated string of the key by logging the result to the console.

Further reading:

RSA encryption and decryption in java

Java AES 256 encryption decryption example

Encrypt a random text

To encrypt the message, create a Cipher object and use the getInstance() with parameter AES/CBC/PKCS5Padding as the transformation to create an instance of the algorithm.

The transformation has a mode and padding, and in our case, we will use CBC mode, which stands for cipher block chaining, and PKCS5Padding as the padding.

The default mode is ECB , but since it does not support multiple blocks of data, we will use CBC , which is a mode of operation for a block cipher.

The cipher block chaining mode uses an initialization vector, also known as IV , which is an input to the cryptographic algorithm used to provide the initial state and requires to be unique.

The padding is introduced to the algorithm so that if the string to be encrypted is not an exact multiple of the block size, then padding is done before encrypting by adding a padding string.

Since we will provide an initialization vector to the init() method of the Cipher create IvParameterSpec class and pass the key bytes to its constructor, which be used as the initialization vector.

Call the init() method and pass Cipher.ENCRYPT_MODE , SecretKey and finally the IvParameterSpec object created.

Create a random text and call the doFinal() method of the Cipher and pass the message bytes to the method to perform encryption.

The doFinal() method returns an array of bytes containing the encrypted message, and we can convert the bytes to string using the encodeToString() method and log its content to the console to verify that the encryption was successful.

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