The block cipher NSABC (public domain)

Alice Nguyenova-Stepanikova; Tran Ngoc Duong

Paper 2011/237

The block cipher NSABC (public domain)

Alice Nguyenova-Stepanikova and Tran Ngoc Duong

Abstract

We introduce NSABC/w – Nice-Structured Algebraic Block Cipher using w -bit word arithmetics, a 4w -bit analogous of Skipjack [NSA98] with 5w -bit key. The Skipjack's internal 4-round Feistel structure is replaced with a w -bit, 2-round cascade of a binary operation (x,z)\mapsto(x\boxdot z)\lll(w/2) that permutes a text word x under control of a key word z . The operation \boxdot , similarly to the multiplication in IDEA [LM91, LMM91], bases on an algebraic group over w -bit words, so it is also capable of decrypting by means of the inverse element of z in the group. The cipher utilizes a secret 4w -bit tweak – an easily changeable parameter with unique value for each block encrypted under the same key [LRW02] – that is derived from the block index and an additional 4w -bit key. A software implementation for w=64 takes circa 9 clock cycles per byte on x86-64 processors.

Note: Terminology correction.

Metadata

Available format(s): PDF
Category: Secret-key cryptography
Publication info: Published elsewhere. Unknown where it was published
Keywords: block ciphers tweakable algebraic modular multiplication IDEA Skipjack
Contact author(s): tranngocduong @ gmail com
History: 2011-05-18: received
Short URL: https://ia.cr/2011/237
License: CC BY

BibTeX

@misc{cryptoeprint:2011/237,
      author = {Alice Nguyenova-Stepanikova and Tran Ngoc Duong},
      title = {The block cipher {NSABC} (public domain)},
      howpublished = {Cryptology {ePrint} Archive, Paper 2011/237},
      year = {2011},
      url = {https://eprint.iacr.org/2011/237}
}