Date Published: December 23, 2024
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Author(s)
National Institute of Standards and Technology
Announcement
The Advanced Encryption Standard (AES) specifies a subset of the Rijndael block cipher family with 128-bit blocks that was submitted to the NIST AES development effort. While this block size remains sufficient for many applications, the increasing demand for processing large volumes of data highlights the potential advantages of a larger block size. This need was pointed out in the public comments received for (Special Publication) SP 800-38A, acknowledged in NIST Internal Report 8459, and further reinforced during two NIST public workshops on block cipher modes of operation.
In August 2024, NIST indicated its interest in vetting another Rijndael variant for approval: Rijndael with 256-bit blocks (i.e., Rijndael-256) with a single key size of 256-bits. NIST plans to develop a draft standard for Rijndael-256 over the next year and requests public comments on this plan by June 25, 2025, especially for the following categories:
- Security analysis, including any new cryptanalytic results related to the 256-bit block size
- Performance and efficiency, particularly in environments with hardware support for AES
Send comments to ciphermodes@nist.gov with “Comments on Rijndael-256” in the subject line. Comments received in response to this request will be posted on this site after the due date. Submitters’ names and affiliations (when provided) will be included, while contact information will be removed.
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