October 16, 2008, 5:40 AM — In my last post I discussed the Advanced Encryption Standard (AES). Another encryption standard is known as RC6. Its predecessors were RC4 and RC5. RC6 is a fast block cipher (cryptographic algorithm) designed by Ronald Rivest for RSA Data Security (now RSA Security) in 1994. RC by the way stands for Ronâ€™s Code and/or Rivestâ€™s Ciphers.
What a block cipher does is take clear text and then operate on chunks of that text known as blocks. The â€œoperates on chunks of that textâ€ means that an algorithm is applied to the block which performs an encryption on the input block using a secret key and outputs a corresponding block of ciphertext. The decryption process is similar in that a block of ciphertext has an algorithm applied to it, using the same secret key and produces the original block of plaintext.
A block cipher differs from a stream cipher, such as RC4, in that a block cipher works on â€œblocksâ€ of cleartext and a stream cipher works on a stream of digits one at a time. Read the rest of this article