Tagged Questions

The cryptographic sponge is a construction scheme for hash functions (and other symmetric primitives) based on an unkeyed permutation. The most famous example is Keccak, which won the SHA-3 competition.

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3
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1answer
83 views

Where did the SHAKEs come from in SHA3?

Where did SHAKE128 and SHAKE256 originate from? I am trying to find them in the original Keccak documentation but can't find them. Is it some special mode of Keccak referenced in the documentation? ...
1
vote
1answer
45 views

SpongeWrap without padding and frame bit

Assuming all inputs are same length as rate except last can be shorter. Is it necessary to pad every input (not just last) to sponge for authenticated encryption to be secure? Is this just, because ...
6
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1answer
201 views

Security analysis of Spritz?

Recently, a new cipher called Spritz has been released by Ronald L. Rivest and Jacob Schuldt. It should be a "drop-in replacement" for RC4. There are many differences to RC4, Spritz is "spongy" and ...
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vote
1answer
219 views

How should I treat a new cipher release like Spritz?

I have been looking at both the paper as well as the sourcecode of Spritz — a spongy RC4-like stream cipher and hash function by Ronald L. Rivest and Jacob Schuldt. The paper states We have also ...
1
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2answers
90 views

Different padding rules for Merkle-Damgard and Keccak/sponge function

We learned that length padding was used in Merkle-Damgard where after padding with zeros another block is added that contains the initial length of the input. This is supposed to prevent same hash ...
3
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1answer
80 views

What is the importance of the $r$ and $c$ values for the Sponge Construction?

What is the importance of the $r$ and $c$ values? Keccak[r=1600,c=0] is stated on a calculator on the Keccak website to be a checksum. But I figured if c=0, then there's only one possible output? ...
4
votes
1answer
95 views

Why has the sponge construction's generic collision finding attack a complexity of O(min(2^(-n/2) , 2^(-c/2)))?

I'm trying to learn about sponge function for creating hash functions and generic attacks on it. I'm looking for the collision finding attack scenario which leads to $O(\min(2^{-n/2} , 2^{-c/2}))$ ...
2
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1answer
196 views

Does SpongeWrap (from the Keccak team) absorb ciphertext or plaintext?

I have been reading the Cryptographic sponge functions paper, but I'm still confused. Does Keccak in authenticated encryption mode absorb ciphertext or plaintext? Edit: Are there any test vectors to ...
4
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2answers
331 views

Using SHA3 as an entropy pool

Has any work been done on analyzing the SHA3 sponge construction for use as an entropy pool (e.g. /dev/random)? All the use cases I've heard of consts of a ...
7
votes
1answer
450 views

Is it possible to actually verify a “sponge function” security claim?

When using a “sponge function” to create a cryptographic hash, we can look at the flat sponge claim, which flattens the claimed success probabilities of all attacks using a single parameter: the ...
8
votes
2answers
1k views

Why are the constants so simple in Keccak?

Keccak, the construction selected for SHA-3 is very interesting. It seems unlike other primitives and has chosen very simple constants. (Keccak talk PDF) The initial values of the state in Keccak is ...
8
votes
2answers
524 views

Why xor the message into the state for sponge hashes?

Sponge hashes like Keccak(SHA-3) and CubeHash, xor a message block into part of the internal state. Why use a reversible operation like xor for that, instead of replacing that part of the state with ...
14
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4answers
1k views

What security do Cryptographic Sponges offer against generic quantum attacks?

In the face of non-quantum attacker, Keccak[r=1088,c=512] with 512 bits of output provides: Collision resistance up to $2^{256}$ operations Preimage resistance up to $2^{256}$ operations Second ...