SMASH (hash)

SMASH
General
Designers	Lars R. Knudsen
First published	2005
Detail
Digest sizes	256 or 512 bits
Best public cryptanalysis
	Collision, Second Preimage

SMASH is a cryptographic hash function which was created by Lars R. Knudsen.^[3] SMASH comes in two versions: 256-bit and 512-bit. Each version was supposed to rival SHA-256 and SHA-512, respectively, however, shortly after the SMASH presentation at FSE 2005, an attack vector against SMASH was discovered which left the hash broken.

Specifications

The message length was limited to less than 2¹²⁸ for SMASH-256 and 2²⁵⁶ for SMASH-512.

Definition

Input: 256/512-bit message blocks $m_{1},m_{2},...,m_{t}$ and $\theta \in GF(2^{n})$

$h_{0}=f(iv)\oplus iv$
$h_{i}=h(h_{i-1},m_{i})=f(h_{i_{1}}\oplus m_{i})\oplus m_{i}\oplus \theta m_{i}$
$h_{t+1}=f(h_{t})\oplus h_{t}$

The function f is a complex compression function consisting of H-Rounds and L-Rounds using S-boxes, linear diffusion and variable rotations, details can be found here ^[3]

Details

The S-boxes in SMASH are derived versions from the Serpent ones.

References

^ Pramstaller, Norbert; Rechberger, Christian; Rijmen, Vincent (2006). "Breaking a New Hash Function Design Strategy Called SMASH". Selected Areas in Cryptography. Lecture Notes in Computer Science. Vol. 3897. pp. 233–244. doi:10.1007/11693383_16. ISBN 978-3-540-33108-7.
^ Lamberger, Mario; Pramstaller, Norbert; Rechberger, Christian; Rijmen, Vincent (2006). "Second Preimages for SMASH". Topics in Cryptology – CT-RSA 2007. Lecture Notes in Computer Science. Vol. 4377. pp. 101–111. doi:10.1007/11967668_7. ISBN 978-3-540-69327-7.
^ ^a ^b Knudsen, Lars R.: SMASH - A Cryptographic Hash Function, Accessed 23 November 2009

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[1] Pramstaller, Norbert; Rechberger, Christian; Rijmen, Vincent (2006). "Breaking a New Hash Function Design Strategy Called SMASH". Selected Areas in Cryptography. Lecture Notes in Computer Science. Vol. 3897. pp. 233–244. doi:10.1007/11693383_16. ISBN 978-3-540-33108-7.

[2] Lamberger, Mario; Pramstaller, Norbert; Rechberger, Christian; Rijmen, Vincent (2006). "Second Preimages for SMASH". Topics in Cryptology – CT-RSA 2007. Lecture Notes in Computer Science. Vol. 4377. pp. 101–111. doi:10.1007/11967668_7. ISBN 978-3-540-69327-7.

[knudsen-3] Knudsen, Lars R.: SMASH - A Cryptographic Hash Function, Accessed 23 November 2009

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