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Questions tagged [sponge]

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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Valid use of extendable output functions?

I'm paranoid about new storage devices, since it's a common scam to reprogram a device to lie and report a much larger capacity than it actually has. I know that there are testing programs ...
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Do you need assembler to enhance the performance of your algorithm?

for an IT-Project in school I'm developing a sponge constrction (doesn't have to be secure but it has to mix well) and I'm done implementing it in Python,however it is extremely slow and I don't ...
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Can f(S) also be replaced by PRP(S) in a Sponge consruction?

I have difficulties understanding the PRP in the absorb phase of a sponge construction: a block is XORed to the r part of the state memory,and then the entire state sent through a blockcipher-like ...
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Is this an example of a sponge construction?

I am having difficulties understanding a sponge construction, as I don't really understand whether the long internal state of a sponge construction is compressed in the squeeze phase, or whether bits ...
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Preimage resistance of sponge-based hashes and XOFs

In the sponge construction for hash functions, including SHA3 and SHAKE, its used a permutation $$f:\{0,1\}^r\times\{0,1\}^c\to\{0,1\}^r\times\{0,1\}^c\\ \;\quad(R,C)\quad\quad\mapsto\quad\;(R',C')$$ ...
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Oribatida masking question

Why Oribatida uses previous capacity $V_{a+m-1}$ instead of current capacity $V_{a+m}$ for rate masking? EDIT: I have asked this one of the authors (Arghya Bhattacharjee) and he replied: Let's say ...
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Sponge capacity feed-forward

Consider Sponge construction where capacity part of state is feed-forward and xor-ed into next state. ${state}_{i+1} = F({{state}_i}^{rate} || {{state}_i}^{capacity}) \oplus (0^{rate} || {{state}_i}^{...
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Full-Block Cipher Feedback Mode as a complete AEAD with a free MAC?

Full-State Keyed Sponge (aka Donkey Sponge) appears to cross over into block cipher mode territory such as Full Block Cipher Feedback Mode: Full State Keyed Sponge (FKS) construction: FKS has been ...
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Can a Full-State Keyed Sponge be used as AEAD by using XEX?

Full-State Keyed Sponge (aka Donkey Sponge) is when a message is absorbed into the full state of the sponge. Such an approach to MAC construction is considered secure. 1 However for an AEAD or a ...
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Are sponges inherently inefficient when compared to other constructions?

A sponge has by definition 'wasted' operations (the part of the state which always remains private but goes through all the ops of the permutation). In return for that waste you get a MAC at the end - ...
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How is the Full-State Keyed duplex useful?

In the Full-State Keyed duplex (sponge construction AEAD), plaintext is absorbed into the entire state of the sponge permutation but only a portion of the output can be used else the scheme breaks (...
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Key blinding security in Ascon

This article explains the role of key blinding in Ascon. Key blinding in Ascon involves XORing the key with the capacity part after the permutation in both the initialization and finalization stages. ...
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Security level of sponge construction based on output and capacity

I was looking at the security level of instances of sponge construction on Wikipedia depicted in the following image. It seems to me that the security level for collision resistance follows the ...
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Sponge construction versus Merkle-Damgard For Hashing based on the very same primitive

I am a bit confused about Sponge construction and Merkle-Damgard-style ones for hashing. The only advantage I see for sponge construction is that they are secure against length extension attacks. So ...
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How is the $\chi$ step of the Keccak permutation invertible?

I would like to understand how Keccak's permutation function is reversible. The difficulty I have is with the $\chi$ step that uses the and operator which is not revertible. All the other ...
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How is the message considered in the STROBE-based Schnorr signature example?

I've been studying the Schnorr signature scheme and recently came across an example that uses the STROBE protocol. In the classic version of Schnorr signatures, the challenge e is calculated as e = H(...
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Which ciphers have been defined that use the Keccak sponge?

There seem to have been defined multiple ciphers using the Keccak sponge as building block / primitive. These seem to have escaped public attention, possibly because they have not been standardized ...
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How do the c-bits (capacity bits) make the sponge construction better?

I know that the message never directly changes those last c bits of the internal state (as seen in the image). And I also know that the capacity bits make the sponge construction resistant against ...
questions change the world's user avatar
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256-bit security with Sponges

Cryptographic sponge functions are a hot topic right now with LWC and all. They solve the symmetric crypto problem with simplicity and efficiency. However, none of them seem to achieve 256-bit ...
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ChaCha-based Sponge PRNG fails PractRand suite

TL;DR: My simple ChaCha-based sponge PRNG is getting "unusual" evaluation from PractRand test battery pretty reliably, sometimes even within the first GB; I'm trying understand why. I was in ...
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Sponge Duplex authenticated encryption with nonce reuse or no nonce

With a Sponge permutation in a Duplex construction for authenticated encryption. illustration example: ascon; actual interest if relevant: keccak Suppose there is no associated data and there is no ...
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Indifferentiability of Sponge Construction

In the case of sponge construction, it is shown to be differentiable from a RO. In the paper by Bertoni et al., what is meant by the node being saturated. How does it become saturated and the ...
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How to implement a basic "sponge function"?

In Chapter 6 of Serious Cryptography, they write about the sponge function: It XORs the first message block, M1, to H0, a predefined initial value of the internal state (for example, the all-zero ...
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Synchronous Sponges

The paper The sponge construction as a source of secure cryptographic primitives (see Figure 6) mentions a synchronous sponge mode (working like CTR or OFB modes). So, this type of sponge is a non-...
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Why does TinyJAMBU-128 claim only 112-bit security?

I am trying to understand the security level of TinyJAMBU-128. As shown in Table 4.1 page 12 of this document, TinyJAMBU-128 claims 112-bit security. However, it has a 128-bit key. How have we lost 16 ...
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Is it possible to create a ciphersuite for TLS 1.3 using only the Keccak-sponge/duplex?

Now that Keccak has been chosen as SHA-3 we see that there have been defined quite a few related modes, including authenticated cipher modes, the KMAC message authentication mode, XOF's and whatnot. ...
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How does KECCAK operate on a state array filled with zeros?

Im trying to implement a sponge in Java. The state starts out as an empty 200 byte array of all zeros. In the KMAC samples document from NIST, the following happens: (black line is a pdf page break) ...
Dustinvonsandwich's user avatar
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Why HAIFA and sponge constructions are not prone to length extension attacks?

I was writing in a document about the flaws of the MD construction which pushed cryptographers to create different and more robust constructions. However, I don't know why HAIFA and Sponge ...
Hinton Zsh's user avatar
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What is the sponge construction in simple terms?

I suggested to my client to use SHA3 instead of SHA2. I know that SHA3 is based on Keccak algorithm which won the NIST's competition. I want to explain the structure of sponge functions in very simple ...
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Absorbing r + c bits in first round of a sponge function

In the standard sponge construction, r bits are consumed in each absorption step, and they get concatenated with c capacity bits....
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What is the rationale design of TinyJambu-LWC?

My understanding of duplex construction is usually initialized with the key at the beginning of the mode, but I have noticed that TinyJambu (in addition to key intilization) is using key in each ...
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Why is the internal chacha20 permutation vulnerable to attacks if used in a sponge construction?

The user Forest in here claims that the internal chacha20 permutation is "vulnerable to attacks if it were used in a sponge construction". My question is as follows: What are these attacks? Would ...
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Sponge with PRF instead of PRP

In most uses of Sponge mode of operations such as SHA3 and many of the round-2 candidates in the NIST lightweight cryptography project, the underlaying primitive is a cryptographic permutation - that ...
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what are the benefits/limits of constructing AEAD using Duplex mode with ARX primitive (chacha20 for example)?

I understand that WAGE cipher uses duplex/sponge mode with stream based cipher for Authenticated encryption with associated data (AEAD) and NORX uses duplex/sponge mode with LRX structure , so , Is ...
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Rationale for NORX/Ketje/Keyak not being chosen for the CAESAR final portfolio

Was any specific rationale given on why none of the sponge-based AEAD algorithms (specifically NORX, Keyak, and Ketje) of the 3rd round candidates of the CAESAR competition made it to the final ...
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SHA-3 Step by step?

Can somebody explain me or give me a link of a step by step SHA-3 explanation it has been really hard for me to undesrtand it. I would love to see an explanation since it's input untill the digest is ...
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Can any hash function based on the sponge construction work as extendable output function?

Keccak provides a sort of very useful XOFs. Can other sponge construction hash function like Spongent work as XOF? Is there any lightweight XOF for hardware or software implementation?
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Random permutation of bit strings of length $n$, where $n$ can be any positive integer?

I need an efficient, invertible random permutation of $n$-bit strings, defined by a $128$-bit key. $n$ can be any positive integer from $6$ to $128$. I have no requirements on the security of the ...
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Capacity bits in SHA-3

I am trying to understand the sponge construction, and in the official web site I found this sentence: The last c bits of the state are never directly affected by the input blocks and are never ...
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Is it possible to apply a pseudo-random permutation (a keyed permutation) to construct a sponge function?

The description of the sponge function on Crypto.Stackexchange contains the following text The cryptographic sponge is a construction scheme for hash functions (and other symmetric primitives) based ...
lyrically wicked's user avatar
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Intuition for SHA3 sponge construction

I would like to get some intuition on the security of the sponge construction. I'm referring to this diagram and notation. Let's consider the case where we have don't apply $f$ in the squeezing ...
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Usage and limitations of sponge functions for PRNG

This HRNG uses SHA3 as a sponge function (in its device driver) to inflate ots raw source output to many MByte/s. They compare this output rate to the output of other HRNG which don't use a sponge ...
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Adding the key in the first state of keyed sponge-based hash function [closed]

What are the advantages to add the key in the inner or outer part of first state in keyed sponge hash functions?
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How can one build $2^{c/2}$ attack on sponge hash?

Let $H$ be a sponge hash with rate $r$ and capacity $c$, built from a permutation $\pi: \{0, 1\}^n \rightarrow \{0, 1\}^n$, where $n = r + c$. Assuming $r \ge 2c$, how can I find a collision with ...
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What are the consequences if someone finds the accessible 1600-bit block $X$ and $R$-bit block $V$ such that $\text{Keccak-}f[1600](X \oplus V) = X$?

Let $H$ denote any hash function based on the sponge construction. Let $F$ denote its underlying function that transforms the $L$-bit state (for SHA-3, $F = \text{Keccak-}f[1600]$ ). Let $R$ denote ...
lyrically wicked's user avatar
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Why is SHA-3 a Sponge function?

A sponge function is supposed to be able to generate an arbitrary length of output. Yet, SHA3 (Bouncycastle) constrains me to choose an output length between 224, 256, 384, and 512. Evidently, these ...
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security of a sponge construction

I don't get why the size of C (the capacity) of a sponge construction influences the security of the sponge construction. And what is the influence of the size of R?
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Is the Keccak family of sponge constructions the same as SHA-3?

I can't seem to come across a clear and to the point answer. Is SHA-3 in the same situation as ElGamal and DSA, where it is modified slightly, or is the original Keccak submission the exact same as ...
Expectator's user avatar
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Is it theoretically possible for the output of SHAKE to be an infinite concatenation of the same 512-bit block?

Let $X$ denote a particular 512-bit sequence. Let $A,B,C$ denote sequences of bits such that: $$len(X || A) = len(X || B) = len(X || C) = 1600$$ $$\operatorname{Keccak-}f(X||A) = X||B$$ $$\...
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Using NIST constructions based on Keccak like cSHAKE128 for other sponges

NIST defines a lot of interesting applications of sponges in FIPS 202 and NIST SP 800-185 like the XOF cSHAKE128 or the MAC scheme KMAC. All this schemes come with a security guarantee and are ...
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