Paper 2026/1818
Blood MERIDIAN: a blockcipher that is not a blockcipher
Abstract
MERIDIAN is a 128-bit blockcipher proposed as a lightweight AES alternative. We show that its “Directional Substitution” layer is not injective by giving an explicit collision. This yields a full 12-round collision for every key. Consequently, no keyed instance of MERIDIAN is a permutation, so no decryption function can invert encryption on all plaintexts, and its blockcipher and PRP security claims fail. We additionally identify a one-round differential that exceeds the claimed bound by a factor 13.37.
Metadata
- Available format(s)
-
PDF
- Category
- Secret-key cryptography
- Publication info
- Preprint.
- Contact author(s)
- jeanphilippe aumasson @ gmail com
- History
- 2026-08-28: approved
- 2026-08-27: received
- See all versions
- Short URL
- https://ia.cr/2026/1818
- License
-
CC0
BibTeX
@misc{cryptoeprint:2026/1818,
author = {JP Aumasson},
title = {Blood {MERIDIAN}: a blockcipher that is not a blockcipher},
howpublished = {Cryptology {ePrint} Archive, Paper 2026/1818},
year = {2026},
url = {https://eprint.iacr.org/2026/1818}
}
