RSA Laboratories

RC6® Block Cipher

The RC6 block cipher was designed by Ron Rivest in collaboration with Matt Robshaw, Ray Sidney, and Yiqun Lisa Yin from RSA Laboratories. The algorithm is an evolutionary improvement over the RC5® block cipher, and like RC5, it makes essential use of data-dependent rotations.

As part of the effort to find the successor to DES, RSA Laboratories submitted RC6 as a candidate for the Advanced Encryption Standard (AES). RC6 entered the final round as one of five algorithms, but the Belgian algorithm Rijndael was eventually selected for the AES.

Yet, RC6 remains an ideal choice for many high-security and high-performance applications. We have prepared a note listing the advantages and disadvantages of RC6 compared to the AES.

To promote RC6 further, RSA Laboratories has submitted the algorithm to the NESSIE project, the NP 18033 project (via the Swedish ISO/IEC JTC 1/SC 27 member body), and the Information-technology Promotion Agency in Japan. See our submissions page for more information.


  • The RC6 Block Cipher, algorithm specification, August 1998 (PDF, 423k)
  • RC6 Object Identifiers (Text File, 2k) NEW

Security and performance evaluation

  • The Security of the RC6 Block Cipher (PDF, 625k - Zipped .PS, 204k)
  • Results of some additional statistical testing on RC6, April 2000 (PDF, 94k)
  • RC6 Performance Statistics (HTML)
  • A comparison between RC6 and the AES (PDF, 110k)

AES presentations and papers

  • Ron Rivest's presentation at the AES conference, August 1998 (PowerPoint, 153k)
  • Presentation from the third AES Workshop, April 2000 (PowerPoint, 38k)
  • Statements on the suitability of RC6 for the AES:
    • Submission to 3rd AES Workshop, April 2000 (PDF, 107k)
    • Final comments, May 2000 (PDF, 269k)

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