In the second approach, the AES secret key can be derived from a given password using a password-based key derivation function like PBKDF2. In the first approach, the secret key should be generated from a Cryptographically Secure (Pseudo-)Random Number Generator like the SecureRandom class. There are two ways for generating a secret key in the AES: generating from a random number, or deriving from a given password. The input data to the AES can be string, file, object, and password-based. In the AES algorithm, we need three parameters: input data, secret key, and IV. So the size of data after encryption is: ciphertext_size (bytes) = cleartext_size + (16 - (cleartext_size % 16))įor storing IV with ciphertext, we need to add 16 more bytes.

Also, in ECB and CBC modes, we should use a padding algorithm like PKCS5. The AES doesn't change the size, and the ciphertext size is equal to the cleartext size. The AES has a block size of 128 bits or 16 bytes.

In this mode, encryption can't be parallelized, but decryption can be parallelized. In the next block, it uses the encryption result to xor with the plaintext block until the last block. Then it encrypts the result to the ciphertext block. First, CBC uses the plaintext block xor with the IV. Here we will only discuss on CBC (Cipher Block Chaining).ĬBC mode uses an Initialization Vector (IV) to augment the encryption. Each mode has its strengths and weaknesses. Moreover, the mode of operation may convert the block cipher into a stream cipher. We can apply the mode of operation in order to strengthen the effect of the encryption algorithm. The AES algorithm has six modes of operation: Padding is the process of filling up the last block to 128 bits. If the data to be encrypted doesn't meet the block size requirement of 128 bits, it must be padded.

The AES algorithm is an iterative, symmetric-key block cipher that supports cryptographic keys (secret keys) of 128, 192, and 256 bits to encrypt and decrypt data in blocks of 128 bits. Many times we require to encrypt some plain-text such as password at the client side (Javascript) and send it to server and then server decrypts it to process further or vice-versa. Hi, in this post we will learn how to implement AES encryption and decryption using the Java and JavaScript.

Block cipher decryption tool aes to cbc