Package org.silverpeas.core.security.encryption.cipher

Class AESCipher

  • All Implemented Interfaces:
    Cipher
    public class AESCipher
extends BlockCipherWithPadding
    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. It has been adopted by the U.S. government and is now used worldwide. It supersedes the Data Encryption Standard (DES), which was published in 1977.

    AES is based on a design principle known as a substitution-permutation network, and is fast in both software and hardware. Unlike its predecessor DES, AES does not use a Feistel network. AES is a variant of Rijndael which has a fixed block size of 128 bits, and a key size of 128, 192, or 256 bits. By contrast, the Rijndael specification per se is specified with block and key sizes that may be any multiple of 32 bits, both with a minimum of 128 and a maximum of 256 bits.

    This implementation provides the encryption and the decryption of text by using the AES algorithm with which the CBC (Cipher Block Chaining) operation mode is applied. With CBC, a random Initialization Vector (IV) is used in order to produce the ciphertext unique; for a same plain text, a different ciphertext can be computed. The resulting encrypted data is then made up of the ciphertext and of the IV used in the encryption. By this way, a different AES cipher implementation cannot decrypt the encrypted data that was computed by this implementation and it cannot decrypt the ciphertext coming from another AES cipher implementation without having the IV combined with the ciphertext.

    The cryptographic tasks in this implementation are based upon the AES cipher provided in the Java Cryptography API. It supports both AES-128, AES-192, and AES-256, depending on the the size of the key passed as argument in the encryption and in the decryption functions. In order to use keys of size above of 128 bits, the Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy Files are required. For each of these size of the symmetric key, a given number of repetitions of transformation rounds that convert the plaintext into the ciphertext is performed:

    • 10 cycles of repetition for 128-bit keys (AES-128)
    • 12 cycles of repetition for 192-bit keys (AES-192)
    • 14 cycles of repetition for 256-bit keys (AES-256)
    Any other sizes will raise a CryptoException exception.