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Second Pre-Draft Call for Comments on SP 800-38D | GCM and GMAC Block Cipher Modes of Operation
NIST is revising Special Publication 800-38D, Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC. The public comment period is open through July 31, 2026.
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 [at] nist.gov (ciphermodes[at]nist[dot]gov) with “Comments on SP 800-38D revision” in the subject field.