What is AES ?
The Advanced Encryption Standard (AES) is a specification for the encryption of electronic data established by the U.S. National Institute of Standards and Technology (NIST) in 2001.[4]
AES is based on the Rijndael cipher[5] developed by two Belgian cryptographers, Joan Daemen and Vincent Rijmen, who submitted a proposal to NIST during the AES selection process.[6] Rijndael is a family of ciphers with different key and block sizes.
For AES, NIST selected three members of the Rijndael family, each with a block size of 128 bits, but three different key lengths: 128, 192 and 256 bits.
Using AES encryption in C#
1. Encrypting data :
The following function takes 3 parameters1-The first parameter is byte array of the data that has to be encrypted .
2-The second parameter is the key that will be used to encrypt the data
3-Third parameter is the initialization vector .
The function returns the encrypted byte array .
AesCryptoServiceProvider :
Performs symmetric encryption and decryption using the Cryptographic Application Programming Interfaces (CAPI) implementation of the Advanced Encryption Standard (AES) algorithm.
CreateEncryptor : This function takes key and IV to create a symmetric encryptor object with the current Key property and initialization vector (IV) . If Key or IV is null the GenerateKey method is called to create a new random Key or IV .
public byte[] encryptdata(byte[] bytearraytoencrypt, string key, string iv)
{
AesCryptoServiceProvider dataencrypt = new AesCryptoServiceProvider();
//Block size : Gets or sets the block size, in bits, of the cryptographic operation.
dataencrypt.BlockSize = 128;
//KeySize: Gets or sets the size, in bits, of the secret key
dataencrypt.KeySize = 128;
//Key: Gets or sets the symmetric key that is used for encryption and decryption.
dataencrypt.Key = System.Text.Encoding.UTF8.GetBytes(key);
//IV : Gets or sets the initialization vector (IV) for the symmetric algorithm
dataencrypt.IV = System.Text.Encoding.UTF8.GetBytes(iv);
//Padding: Gets or sets the padding mode used in the symmetric algorithm
dataencrypt.Padding = PaddingMode.PKCS7;
//Mode: Gets or sets the mode for operation of the symmetric algorithm
dataencrypt.Mode = CipherMode.CBC;
//Creates a symmetric AES encryptor object using the current key and initialization vector (IV).
ICryptoTransform crypto1 = dataencrypt.CreateEncryptor(dataencrypt.Key, dataencrypt.IV);
//TransformFinalBlock is a special function for transforming the last block or a partial block in the stream.
//It returns a new array that contains the remaining transformed bytes. A new array is returned, because the amount of
//information returned at the end might be larger than a single block when padding is added.
byte[] encrypteddata = crypto1.TransformFinalBlock(bytearraytoencrypt, 0, bytearraytoencrypt.Length);
crypto1.Dispose();
//return the encrypted data
return encrypteddata;
} Decrypting data :
The following function takes 3 parameters1-The first parameter is byte array of the data that has to be decrypted .
2-The second parameter is the key that will be used to decrypt the data
3-Third parameter is the initialization vector .
The function returns the decrypted byte array .
private byte[] decryptdata(byte[] bytearraytodecrypt, string key, string iv)
{
AesCryptoServiceProvider keydecrypt = new AesCryptoServiceProvider();
keydecrypt.BlockSize = 128;
keydecrypt.KeySize = 128;
keydecrypt.Key = System.Text.Encoding.UTF8.GetBytes(key);
keydecrypt.IV = System.Text.Encoding.UTF8.GetBytes(iv);
keydecrypt.Padding = PaddingMode.PKCS7;
keydecrypt.Mode = CipherMode.CBC;
ICryptoTransform crypto1 = keydecrypt.CreateDecryptor(keydecrypt.Key, keydecrypt.IV);
byte[] returnbytearray = crypto1.TransformFinalBlock(bytearraytodecrypt, 0, bytearraytodecrypt.Length);
crypto1.Dispose();
return returnbytearray;
} 