Introduction to AES

AES Key Generator Devon 2019-04-27T15:14:21-07:00. Below is a Base64 Encoded AES-256 key which was been generated using the secure javax KeyGenerator. This key will work perfectly with any of the AES encryption code elsewhere on my site, and probably most of yours as well. This key is secure, randomly generated, and has been generated just for you. AES Example - Input (128 bit key and message) Key in English: Thats my Kung Fu (16 ASCII characters, 1 byte each) Translation into Hex: T h a t s m y K u n g F u. AES (Rijndael) online encryption. It is a symmetrical block cipher algorithm (the block size is 128 bits, the key is 128/192/256 bits). AES is a subset of the Rijndael cipher developed by two Belgian cryptographers, Vincent Rayman and Joan Damen. 128-bit encryption is a data/file encryption technique that uses a 128-bit key to encrypt and decrypt data or files. It is one of the most secure encryption methods used in most modern encryption algorithms and technologies. 128-bit encryption is considered to be logically unbreakable. I am doing AES Key Generation in c# and passing the key generated for AES 128 bit Encryption. The case is while generating the key I am getting byte length as 16 while the key string length is getting higher than 16. While trying online I am getting length as 16 itself. What I have tried: Core Code is as below: AES Key 128 bit Generation.

The AES encryption is a symmetric cipher and uses the same key for encryption and decryption. The AES algorithm supports 128, 192 and 256 bit encryption, which is determined from the key size : 128 bit encryption when the key is 16 bytes, 192 when the key is 24 bytes and 256 bit when the key is 32 bytes.

The methods provided by the library accept also a string password instead of a key, which is internally converted to a key with a chosen Hash function.

The optional initialization vector (IV) size is 16 bytes, which is the block size of the algorithm. This is summarized in the table below:

Key sizeAES encryption
16 bytes (128 bits)128 bit encryption
24 bytes (192 bits)192 bit encryption
32 bytes (256 bits)256 bit encryption
IV size:16 bytes

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Padding and Block modes

The Padding and Block mode are important settings for the AES class, that affect the produced encrypted output.

The Padding is used to align the input data to the algorithm BlockSize (16 bytes). The default is PKCS7.

The Block Mode determines what transformation is performed on each processed block. The default one is CBC. It is very important to know what block mode was used for encryption, in order to be able to decrypt it! For example if we know that the encryption has used CTR block mode, we shall set the class to use that mode before decrypting:

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AES encrypting and decrypting a String

The example below shows how to AES encrypt and decrypt a String with a byte array key, with a password and by using or not the optional initialization vector (IV).

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Encrypting and Decrypting a File

The file encryption is performed by calling the methods AES.EncryptFile. The decryption is through the DecryptFile methods respectively:

VB.NET example

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AES Encrypting and decrypting a Stream

The Stream encryption is performed by reading the data from a Stream opened for reading and writing the encrypted output to a Stream that accepts write operations. After the method execution, the output Stream Position will be at the end of the encrypted data.

C# code

VB.NET code

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Encrypting and Decrypting a Byte array

The EncryptBytes and DecryptBytes methods accept byte array as input and return the output as byte array. The example below demonstrates the four possibilities for AES key and initialization vector (IV) offered by the library:

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C# example

VB.NET example

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Exception handling

During the AES encryption and decryption operations errors can appear. In order to handle them more gracefully, the library offers a set of typed exceptions that can help us identify the cause of the error.

Below is an example class that demonstrates the various exceptions that can be expected during encryption and decryption. The methods that deal with files and streams of course may also throw System.IO.IOException sub classes:

C# code

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VB.NET code


Aes Key Gen

This chapter illustrated how to perform AES encryption and decryption with the help of NCiphers.Crypto library.

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