Second Pre-Draft Call for Comments on SP 800-38D | GCM and GMAC Block Cipher Modes of Operation

As previously announced, NIST is revising Special Publication (SP) 800-38D, Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC. In addition to revising the Galois/Counter Mode (GCM), NIST proposes to specify a wider variant, wGCM. wGCM operates on an underlying block cipher with 256-bit blocks, to support the Rijndael-256 variant of AES that NIST proposed for standardization.

NIST is preparing an initial set of parameters for wGCM and requests feedback on the efficiency and security trade-offs. See today’s full announcement for our specific issues and questions.

The public comment period is open through July 31, 2026. Comments can be submitted to ciphermodes@nist.gov with “Comments on SP 800-38D revision” in the subject field.

NIST Cybersecurity and Privacy Program
Questions and comments can be directed to: ciphermodes@nist.gov
CSRC Website questions: csrc-inquiry@nist.gov