Admin: Created page with "A rebound attack that presents collisions against 4 rounds of Kupyna-256 in 2⁶⁷ time and against 5 rounds in 2¹²⁰ time. It was created to replace an..."

2019-06-07T05:17:57Z

Created page with "A rebound attack that presents collisions against 4 rounds of Kupyna-256 in 267 time and against 5 rounds in 2120 time. It was created to replace an..."

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A [[rebound attack]] that presents collisions against 4 rounds of Kupyna-256 in 267 time and against 5 rounds in 2120 time. It was created to replace an obsolete [[GOST (hash function)|GOST]] hash function defined in the old standard GOST 34.11-95, similar to [[Streebog]] hash function standardized in Russia.

In addition to the hash function, the standard also describes [[message authentication code]] generation using Kupyna with digest sizes 256, 384 and 512 bits.

==Description==

Kupyna hash function uses [[Davies–Meyer]] compression function based on [[Even–Mansour cipher]]. The compression function consists of two fixed permutations, T⊕ and T+, which are taken from the [[Kalyna (cipher)|Kalyna]] block cipher and consist of four operations: AddRoundConstant, SubBytes, ShiftBytes and MixColumns. The round function uses four different [[S-box]]es.

The function can return a digest of arbitrary length from 8 to 512 bits; function which returns n-bit digest is called Kupyna-n. The recommended digest lengths are 256, 384 and 512 bits.

The designers claim that [[differential cryptanalysis|differential]] and [[rebound attack|rebound]] attacks are ineffective after 4 rounds of the compression function.

''Kupyna'' is Ukrainian name for ''[[Polygonatum odoratum]]''.

==Examples of Kupyna hashes==
Hash values of empty string.
Kupyna-256("")
0x cd5101d1ccdf0d1d1f4ada56e888cd724ca1a0838a3521e7131d4fb78d0f5eb6
Kupyna-512("")
0x 656b2f4cd71462388b64a37043ea55dbe445d452aecd46c3298343314ef04019 \
bcfa3f04265a9857f91be91fce197096187ceda78c9c1c021c294a0689198538

Even a small change in the message will (with overwhelm probability) result in a mos different hash, due to the [[avalanche effect]]. For example, adding a period to the end of the sentence:
Kupyna-256("The quick brown fox jumps over the lazy dog")
0x 996899f2d7422ceaf552475036b2dc120607eff538abf2b8dff471a98a4740c6
Kupyna-256("The quick brown fox jumps over the lazy dog.")
0x 88ea8ce988fe67eb83968cdc0f6f3ca693baa502612086c0dcec761a98e2fb1f

==Cryptanalysis==
Christoph Dobraunig, Maria Eichlseder, and Florian Mendel describe a collision attack using [[rebound attack]] on Kupyna-256 reduced to 4 rounds with time complexity 267 and on Kupyna-256 reduced to 5 rounds with time complexity 2120, based on rebound attacks on [[Grøstl]].

Jian Zou and Le Dong also describe a collision attack on Kupyna-256 reduced to 5 rounds with time complexity 2120, as well as pseudo-preimage attack on 6-round Kupyna-256 with time and memory complexities 2250 and on 8-round Kupyna-512 with time and memory complexities 2498. They note that these attacks do not threat any security claims of Kupyna.

Onur Duman published [[differential fault analysis]] on Kupyna when it is used for MAC schemes. According to the paper, recovering one byte of the state requires 2.21–2.42 faults.

==Source==

[http://wikipedia.org/ http://wikipedia.org/]
==See Also on BitcoinWiki==
* [[Buglab]]
* [[Novello Technologies]]
* [[CRWD Network]]
* [[AREF]]
* [[Time Money]]

Kupyna - Revision history

Admin: Created page with "A rebound attack that presents collisions against 4 rounds of Kupyna-256 in 267 time and against 5 rounds in 2120 time. It was created to replace an..."

Admin: Created page with "A rebound attack that presents collisions against 4 rounds of Kupyna-256 in 2⁶⁷ time and against 5 rounds in 2¹²⁰ time. It was created to replace an..."