Questions tagged [lattice-crypto]
Lattice-cryptography is the study and use of lattice problems applied to cryptography.
643 questions
1
vote
1
answer
139
views
Do you know any library for implementing lattice-based schemes? [closed]
Good afternoon! I'm trying to write a code for a lattice based scheme (based on the SIS problem).
I'm looking for a library that may help me in this task without taking care of the implementation of ...
- 11
1
vote
1
answer
209
views
Decision LWE vs Search LWE: Which one is harder?
Sometimes if we have an attacker who's able to solve decision-LWE problem then we can use them (as a sub-routine) to solve (search) LWE problem, i.e., $\mathsf{sLWE} \leq \mathsf{dLWE}$.
Conversely, ...
- 586
0
votes
0
answers
135
views
Approximate SIVP worst-case hardness: proper mathematical formulation used for cryptographic purposes
Is the following a correct formulation for the assumed worst-case hardness of $SIVP_\gamma$?
For every PPT algorithm $A$
for every $n\in\mathbb{N}$ there exists a basis $B_{n,A}=\{v_1,\dots,v_n\} \in ...
2
votes
0
answers
65
views
What's the lattice dimension of the uSVP for attacking CRYSTALS-Dilithium-128?
I am trying to understand the process of transitioning from a NIST standard to the attacks based on of the Unique Shortest Vector Problem (Unique-SVP). Specifically, I am working with Crystals ...
- 324
2
votes
1
answer
241
views
Do we know that LWE is harder than Ring LWE?
The plain, normal-form, decisional LWE problem over $\mathbb{Z}/q\mathbb{Z}$ is: given a uniformly random $n\times n$ matrix $A$ and vector $b\in \mathbb{Z}/q\mathbb{Z}^n$, decide if $b=As+e$ for ...
- 1,614
1
vote
2
answers
213
views
Definition of Dual Lattice
1- Can someone explain why we have the definition of dual of a lattice like
$\Lambda^*=\{\vec{v}\in span(\textbf{B}): \langle \vec{v},\vec{x} \rangle \in \mathbb{Z}, \forall \vec{x} \in \Lambda\} $.
2-...
- 586
2
votes
1
answer
111
views
Arithmetic in Cyclotomic Number Rings with Shoup's Number Theory Library (NTL)
I wish to do arithmetic on elements in an integer subring of a cyclotomic number field, i.e, in $\mathcal{O}_K = \mathbb{Z}(\zeta) \cong \mathbb{Z}[X] / <\phi_m(x)>$ where $\zeta$ is a root of ...
- 678
1
vote
0
answers
113
views
Understanding Gentry's initial FHE construction based on ideal lattices
I am trying to understand the encryption procedure in Craig Gentry's initial construction for FHE described in Fully Homomorphic Encryption Using Ideal Lattices. Unfortunately after repeated attempts ...
- 111
6
votes
1
answer
350
views
NTRU Cryptosystem: Why "rotated" coefficients of key f work the same as f
In the NTRU cryptosystem, we can use a randomly generated polynomial f that is inversible under modulo p and q to encrypt and decrypt our plaintext. While studying this system, I attempted to ...
- 175
1
vote
0
answers
95
views
Where do we put known bits of nonce when performing lattice attack on ECDSA?
I have read so many papers and posts about lattice attacks on ECDSA but none of them used an example of different MSB values for k but instead they all used fixed MSB.
So here i am trying to ...
0
votes
0
answers
62
views
Is BGV encryption using different secret keys indistinguishable?
Assume that the same message is encrypted using two different keys within the BGV encryption scheme. Can we assume that the resulting ciphertext are indistinguishable?
I.e., given $c_1 = \text{Enc}(...
- 371
1
vote
1
answer
142
views
Is there an efficient way to check if a lattice has a point with all non-zero components?
Given a basis $\{v_1,\dots,v_k\}$ for a $q$-ary lattice $L$ in ${\mathbb Z}_q^n$, is there an efficient (deterministic/randomized) way to find a point in $L$ with all non-zero components, or decide ...
- 11
1
vote
1
answer
196
views
True Lovàsz condition and definition of a LLL-reduced basis
I am studying the Shortest Vector Problem and I have some troubles understanding the actual Lovàsz condition used in the LLL algorithm.
On the one hand, the original LLL article, the Springer book &...
- 23
3
votes
1
answer
171
views
Differences between the theory and implementation of a lattice attack against ECDSA
I know the theory of lattice attacks against ECDSA from Minerva. So, as far as I can understand, the lattice that they build is
$$
L_M = \begin{bmatrix}
2^ln & 0 & 0 & \cdots & 0 & ...
- 31
0
votes
0
answers
41
views
Non-lattice NIST candidates affected by SVP problems
I would like to know if there are non-lattice based NIST submissions that are affected by a polynomial time algorithm to Shortest Vector Problem. Are there known reduction from (e.g.) code based ...
- 324
1
vote
1
answer
125
views
Why the refresh (modulus and key switching) is required in BGV after addition?
I am reading the BGV paper. On page 18, after addition, the protocol will also refresh (modulus and key switching), may I ask why is this required? It seems to me that I can still use the same secret ...
- 371
1
vote
0
answers
44
views
Is there a many-to-one reduction from GapSVP to GapCVP?
I was wondering if by now any poly-time Karp reduction between GapSVP and GapCVP (exact or approximate) exist. I know of the Cook reduction between these problems, but I couldn't find anything about ...
- 33
0
votes
0
answers
94
views
[About choosing params in BGV like ciphertexts]
I am new to lattice-based cryptography, so sorry that this question might seems stupid
May I ask that how can I choose the BGV parameter of ciphertext with plain text in mod 128, and error in ...
- 371
1
vote
0
answers
115
views
Estimating BKZ block size in Kyber
In Section 5.2.1 of the Kyber documentation, it states that the BKZ block size of 413 was chosen using the tool from this paper, i.e., this tool. How was the block size derived from this? Currently, ...
- 1,614
1
vote
1
answer
122
views
How to set the variance of LWE when using the lwe estimator
based crypto
And I would like to use the lwe estimator to calculate bound for ring LWE
Found in this issue It seems to me I can set up parameters like params = LWE.Parameters(n=2^14, q=2^438, Xs = ...
- 371
1
vote
2
answers
166
views
About multiply by constant of LWE
I am new to lattice-based cryptography
May I ask that for a lattice-based encryption
$$enc(m) = A^{T}R+m \bmod q$$
If I set the $q$ to be able to decrypt to $m$ (and suppose the bound of $q$ is tight ...
- 371
2
votes
1
answer
99
views
in NTRU, can g be recovered given f and h?
The NTRU key generation involves polynomials and their arithmetic in polynomial rings, which is a bit different from arithmetic in modular integers.
In the NTRU cryptosystem, the public key $h$ is ...
- 23
2
votes
0
answers
243
views
Can lattice attack work MSB or LSB are unkown but 16 bytes of private key are known?
I have been reading about lattice attack on ECDSA when partial bits of nonce are known for amount of signatures, So i went through some source code trying to understand how it works.
First of all, ...
8
votes
2
answers
2k
views
Is lattice encryption susceptible to Grover's algorithm?
So Grover's algorithm, also known as the quantum search algorithm, can find an entry, with a high probability, in an unstructured database.
Well can't we consider the basis of a lattice problem an ...
- 355
1
vote
1
answer
104
views
Finding two inputs [i, j] of a custom Hash function where their Hashes are [H(i), H(j)] = [H(i), H(i)^2] [closed]
I came upon the following hash function (pseudo-code):
...
- 33
2
votes
1
answer
318
views
Computing the intersection of two lattices
Given two lattices $L_1$ and $L_2$ represented by bases $B_1$ and $B_2$, is there an efficient algorithm to compute $L_1\cap L_2$?
I can show, I think, that if $\gcd(\det(B_1),\det(B_2))=1$, then $...
- 1,614
0
votes
1
answer
194
views
Discrete Gaussian distribution on a lattice vs. the periodic Gaussian function on a lattice
Gaussian distribution on lattices generally seems esoteric (at least for me, for now). My question is:
Does Gaussian distribution on a lattice mean to add a Gaussian noise on a single point of a ...
- 586
1
vote
2
answers
67
views
[Questions about a proof in the prelim of paper "Lattice-Based Zero-Knowledge Proofs and Applications"]
May I ask that in section 2.7 challenge space in the paper Lattice-Based Zero-Knowledge Proofs and Applications:
Shorter, Simpler, and More General
What is rot(c), why does rot(c) $\in Z^{d*d}$, and ...
- 371
2
votes
1
answer
95
views
$\epsilon$ parameter choice in lattice-based schemes
I am trying to implement Pei10 and BB13, but I am confused about what concrete parameters to use.
In Pei10, Algorithm 1 takes a rounding parameter $r = \omega(\sqrt{\log n})$ as parameter, but it does ...
- 365
1
vote
0
answers
54
views
[About parameters effect LWE and SIS to be computation or perfect secure]
Hello I am new to lattice cryptography
I am reading the paper More Efficient Commitments from
Structured Lattice Assumptions
They define bound B in page 3
Then In figure 1 in page 9
Can ...
- 371
2
votes
1
answer
131
views
Question about the description from ring SIS to SIS in the survey paper: A Decade of Lattice Cryptography
I am currently reading "A Decade of Lattice Cryptography"
At page 30, section 4.3.2, it descrip left multiplication by any fixed ring element a
It mention something about curcilant matrix ...
- 371
3
votes
1
answer
319
views
Kyber-CCA-KEM - Deterministic implicit rejection
In Kyber-CCA-KEM, there's a step in the Fujisaki-Okamoto transformation, where decryption failure results in a random shared secret returned from the decapsulation call.
I have a C language project ...
- 9,795
1
vote
0
answers
111
views
Literature on (concrete) hardness of Short Integer Solution (SIS)
I am interested in what the state of the art results on the hardness of the Short Integer Solution (SIS) instances are. The one I am the most familiar with (and the most discussed) is to use lattice ...
- 365
1
vote
1
answer
205
views
learning with errors
If I talk about efficiency of system of learning with error, is it it fine for q to be composite in Z_q, the ring of integers. As when q would not be prime, Z_q will not be field anymore, won't it ...
- 93
1
vote
1
answer
120
views
Can you instantiate Ring-LWE with coefficients from a prime-power field?
Generally, we instantiate Ring-LWE with the polynomial ring $R = \mathbb{F}_q\ /\ (X^N+1)$ for prime $q$ and some power-of-two $N$.
Can we instead do Ring-LWE over the ring $R = \mathbb{F}_q\ /\ (X^N+...
- 11
2
votes
1
answer
242
views
Why use small error vectors in LWE instead of big ones?
In LWE systems, why is it recommended to add only small error vectors to the system of equations and not big error vectors? Can someone come up with an example?
- 93
1
vote
0
answers
61
views
Misuse Attacks on Lattice Crypto
I've been reading "Misuse Attacks on Post-Quantum Cryptosystems" (https://eprint.iacr.org/2019/525). In what scenarios are the attacks described in the paper applicable? Is it specifically ...
- 423
4
votes
2
answers
386
views
LWE and distributions
In LWE, the error term $e$ is "classically" obtained from the discrete normal distribution. Why is it so often found that this distribution is used? Are there other possibilities for ...
- 95
0
votes
0
answers
55
views
Does randomization make a big difference in the output of the BKZ algorithm?
We all know that block Korkine-Zolotarev (BKZ) algorithm is essentially a deterministic lattice reduction algorithm. However, in the actual implementation, the BKZ algorithm contains some ...
- 311
3
votes
1
answer
122
views
Trapdoor Quality for Lattice Crypto
In these two papers the authors mention the "quality" of a trapdoor
[GPV] https://eprint.iacr.org/2007/432
[MP] https://eprint.iacr.org/2011/501
But the best detail on this matter I could ...
- 217
1
vote
1
answer
160
views
Matrix multiplication circuit
I am trying to understand which operations are computable by an $\texttt{NC}^1$ circuit. However, I am struggling to understand whether there is such a circuit for multiplying a matrix with a vector ...
- 21
6
votes
4
answers
1k
views
Why Module-LWE and not Ring-LWE?
I am trying to understand the NIST-submissions for post-quantum cryptography a bit better, and I noticed that the submissions from the CRYSTALS-family in particular is based on Module-LWE.
I ...
- 61
2
votes
1
answer
91
views
Sigma parameter from Trapdoors for Lattices
In the document Trapdoors for Lattices, section 5.4 Gaussian Sampling, they introduce the parameter $\sqrt{\Sigma_{\bf G}}$, which is related to the lattice $\Lambda^\perp(\bf G)$. They use it as a ...
- 217
0
votes
1
answer
63
views
Finite index quotient group, lattice crypto
A $m$-dimentional full-rank integer lattice $\Lambda\in\mathbb{Z}^{m}$ can be defined as the set of all integer linear combinations of $m$ linearly independent over $\mathbb{R}$ basis vectors $\textbf{...
- 586
1
vote
1
answer
168
views
Post-quantum secure trapdoor function
I am looking for examples post-quantum secure trapdoor functions. Ideally, the inversion knowing the trapdoor should be "simple" in the sense that it can be computed by a circuit in NC^1.
- 21
3
votes
1
answer
395
views
KYBER.CPAPKE: IND-CCA Security of Lyubashevsky, Peikert, Regev (LPR) Encryption
The NIST Kyber KEM spec. defines an encryption scheme, KYBER.CPAPKE, that's a variant of the so called Lyubashevsky, Peikert, Regev ("LPR") encryption scheme [1]. While LPR encryption is ...
- 678
0
votes
1
answer
45
views
About learning with error rings with only constant coefficient
I am new to RLWE, would like to ask whether what I am thinking make sense
Suppose I have a message e.g.: x=5
And I have a lattice based encryption scheme, e.g.: BGV
could I encrypt x with BGV by ...
- 371
1
vote
1
answer
131
views
How does big Galois groups yield better security in NTRU Prime?
I'm still kinda new to Galois theory so I apologize if this question is very obvious to some people.
Basically I'm reading this paper by the NTRU Prime team and in section 2.5 it's explaining how ...
- 13
2
votes
1
answer
186
views
LLL on Knapsack-eque problem
Given integers $s_1, \dots , s_n$ and target integer $t$, I'm trying to find small integer coefficients $x_1, \dots , x_n$ such that:
$$
t \approx x_1 s_1 + \dots +x_ns_n
$$
Taking inspiration from ...
- 123
1
vote
1
answer
109
views
On the spectral norm in lattice-based cryptography
In the preliminaries section of a paper$^\color{magenta}{\star}$ on lattice-based cryptography, the matrix norm $\| \cdot \|_{2}$ is used. Why do we define such norm? What's the purpose of defining ...
- 586