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Questions tagged [elliptic-curves]

Elliptic curves are algebraic-geometric structures with applications in cryptography. Such a curve consists of the set of solutions to a cubic equation over a finite field equipped with a group operation. Questions relating to elliptic curves and derived algorithms should use this tag and might also consider more specific tags such as discrete-logarithm and ecdsa.

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EC non-shared cryptosystems - different group for every party

Efficient Identity Based Parameter Selection for Elliptic Curve Cryptosystems by Arjen K. Lenstra contains a proposal for a non-shared elliptic curve cryptosystem. Every party chooses its own field ...
0
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1answer
23 views

Does Proxy re-encryption can re-encrypt large data?

Many resources talk about the benefit of Proxy Re-encryption (PRE) and I also implement my PRE using Elliptic Curve key pair. But after I set up Global parameters, I can encrypt very small data maybe ...
2
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1answer
62 views

Generating a key pair using a signature generated by an existing key

I’ve built an app in which each user has a private/public key pair and I want to generate a second one for them, however I cannot store the second private key anywhere. What would be the drawbacks ...
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0answers
39 views

Reason for including the public key of the key agreement in the KDF

I found the following text when looking up KDFs: In comparison, the so-called DHAES mode in IEEE 1363a mandates to use the binary representation of the sender’s public key as an input parameter. ...
2
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1answer
46 views

Generating a small EDDSA curve

I have an application that would benefit from very small (e.g. 16-20 byte) EDDSA keys and small signatures. It's an application where the goal is more to deter DOS attacks than "hard" security, so ...
-1
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1answer
52 views

Equivalence of cryptographic problems

Are integer factorization, discrete log and ECDH problems equivalent? I know that factorization and discrete log are equivalent but are one of those two problem equivalent with ECDH? Cand someone ...
-1
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0answers
29 views

Is simple EC arithmetics enough to construct security proofs?

Using the simple rules of modular arithmetics for Elliptic Curves, including associative and commutative rules for $+$ and $*$, where uppercase letters are points and lowercase are scalars on the ...
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0answers
54 views

Is RSA in decline across the board?

From what I gather from the internet (source), the recommended practice for 2019 and beyond is to avoid RSA and use ECDH and ECDSA. Is this the general case?
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0answers
48 views

Finding $P$ when we know $2\times P$ in given Elliptic Curve [duplicate]

For a given elliptic curve $E$ like this $y^2 = x^3 + Ax + B \pmod p$, can we find the point $P$ if we know that the $Q = 2\times P = (a, b)$? For example $E:\ y^2 = x^3 + x + 1 \pmod {10007}$, we ...
6
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0answers
58 views

Is it important to defend against key substitution attack in ECDSA?

When planning a file signature scheme (basically, just to sign all files content). Is it obligatory to defend against ECDSA key substitution attack? ISO/IEC 14888-3:2018 NOTE 5 states: The ...
-2
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1answer
46 views

Elliptical Curve Actual Encryption

Im havirng a had time understanding ECC. For example, I have the equation below: ...
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0answers
37 views

How to do the shortcut function in ECC when N (Private Key) is Known

When N or private key is known, we don't have to iterate through all the process just to get the final location given the two initial points. How is that shortcut function implemented given the ...
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0answers
61 views

ECC: Counting points on $E:y^2+xy= x^3+5x+6$ over $GF(2^3)$

How to exactly count the number of rational points on the elliptic curve over the $GF(2^3)$ where the curve equation is $$E:y^2+xy= x^3+5x+6$$
1
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1answer
54 views

How can you derive a P-256 public key from the X and Y points

Deriving a secp256k1 public key is also possible. For whatever reason, I'm only being provided X and Y, not the public portion. I just need to get the binary representation of the public key given ...
4
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3answers
420 views

Pedersen commitment in elliptic curves

I try to understand Pedersen commitment in elliptic curves over finite fields. I could use some clarification. Let's say we have two generators $G$ and $H$. Is that required that $G$ and $H$ are ...
2
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0answers
29 views

Precomputation attacks against ECDH

Diffie-Hellman groups are vulnerable to sieving precomputation attacks. These attacks allow a one-time computation against a given DH modulus that makes it practical to attack all subsequent key ...
3
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1answer
127 views
+50

What is this EC key derivation method called?

I'm looking to identify the EC key derivation method used in Hyperledger Fabric. I can't find anything in the docs or the protocol specs, but the functions' code is here for the private key and the ...
12
votes
2answers
656 views

What motivated the creation of RSA and ECDH?

Recently I've been learning about cryptography and so far I am loving it. However, there are some things I do not comprehend. As far as I know, RSA was published in 1979 while New Directions on ...
6
votes
2answers
633 views

Is it possible to derive a public key from another public key without knowing a private key (Ed25519)?

I have a following use case: User has his master public (sk) - private (pk) key pair (Ed25519). In DB we store a public key. Is ...
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0answers
54 views

Patterns in elliptic curve division polynomials

While looking at division polynomials of elliptic curves in relation to this and this questions, I noticed some patterns. I am wondering if anyone knows of general formulas the describe these patterns....
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0answers
26 views

Hash function a ring-signature-based range proof

For a ring-signature-based range proof (e.g. Ring Confidential Transactions , section 5.0.1) it is required to use some hash function from $\{0,1\}^* \to \text{scalar}$. Is it safe to take for this ...
3
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0answers
26 views

EC-ELGAMAL message mapping

I have been able properly set up an EC-elgamal protocol by using algorithms available in an IP that I have developed. Everything works fine, except for the fact that I haven't been able to completely "...
1
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1answer
57 views

Can specific Weierstrass curves be some benefit from Montgomery/Edward form?

I have noticed that DBL/diffadd in Edward/Montgomery form almost double fast than Weierstrass form(EFD), and curve25519 is empressive high-performance.The transformation between these forms can be ...
2
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0answers
40 views

ECC - complex multiplication and key agreement

I'd like to ask three questions - 2 of them regard CM method. The last is regarding the ECC domain parameters generation on the fly, see https://eprint.iacr.org/2015/647.pdf What role has ...
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0answers
43 views

Differential representation of binary curve as a public key

Given elliptic curve $E$ over binary field $k$, a public key is the pair $(x,y)$ in $E$ and $x$ and $y$ in $k$. The differential representation of $(x,y)$ is $w = x + y$. What security implications ...
0
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1answer
42 views

Simplified ECC non-point public key example, how it works

I know that ECC public key is in fact point on curve calculated by $(x,y) = k \times G$ , while $k$ is random and $G$ is the base point, it performs "Point addition" which involves some math behind. ...
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1answer
70 views

How to Find the Generators of an Elliptic Curve

Could someone explain how can I find the generator points of an elliptic curve? For example the generators of the EC: $y^2= x^3+x+6, Z_7$.
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0answers
86 views

Using division polynomials to prove that EC discrete log is even

This question is related to the other question I recently asked. I'm trying to figure out if it is possible to use division polynomials to prove that knowing $A = a \cdot G$ we can prove that $a$ is ...
1
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1answer
68 views

CSIDH: Why do we need ideals in the form of $\langle \ell, \pi \pm 1 \rangle$ in order to apply Vélu's formulas when computing the action?

I am trying to understand the action of the CSIDH protocol. Let $E_0:y^2=x^3+ax^2+bx$ be a Montgomery elliptic curve over $\mathbb{F}_p$ for some prime $p$. If we take $\mathcal{O}$ as $End_{\mathbb{...
2
votes
1answer
59 views

Elliptic curve as a product of 3 cyclic groups possible?

I'm looking for some kind of 3-dimensional Elliptic curve. As far as I know a normal Elliptic curve like $$y^2 = x^3 + ax + b$$ over $F_p$ consists of one or two cyclic groups $Z_m (\times Z_n)$. ...
3
votes
1answer
67 views

Elliptic curves on finite fields

I've been reading: https://github.com/bellaj/Blockchain/blob/6bffb47afae6a2a70903a26d215484cf8ff03859/ecdsa_bitcoin.pdf On page 22 it shows an eliptic curve over F17. I have added the orange lines ...
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0answers
50 views

Sharing secret content with multiple recipients

I have a sender and N recipients, and am thinking of using the following scheme to send secret content to those recipients. This is similar context to a group chat or email. I am no expert in crypto ...
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1answer
79 views

What is the difference between subtracting the modulus from a scalar field element and reducing it?

When implementing a Field element, we define the necessary operations on the data structure. One function that I see is a "scalar reduce" function, which effectively reduces a random scalar so that ...
3
votes
2answers
123 views

Prove I know a value $v$ in a Pedersen Commitment without revealing it

Given a Pedersen Commitment: $P = aG + vH$ Where $G$ and $H$ are points in some group. $a$ is a blinding value/mask and $v$ is the value I wish to commit to. Is there a way to prove I know $v$ ...
2
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2answers
103 views

How to model a miniature elliptic curve?

For educational purposes I would need to work on an elliptic curve that has a small field, but holds the safety futures of a real curve. Is that possible to have such a curve!? For example for the ...
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1answer
58 views

Why only non-prime order fields have small subgroup attacks?

Why don't prime-order curves have small subgroup attacks? It seems that I can choose a Generator such that it has a small order, maybe 2 points, and so an attack could generate all of the points in ...
3
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1answer
70 views

What type of curves have co-factors?

I read that non-primes only have co-factors, but Edwards have a co-factor and it is defined over Fp s.t. P = 2^255 -19 which is prime right? How is the co-factor created, some have co-factor 4 and ...
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1answer
44 views

For an elliptic curve, what is the difference between the base field modulus $Q$ and subgroup $r$

What is the difference between the basefield modulus $Q$ and a subgroup of prime order $r$? They are all fields, but what is their relevance to the curve they are defined upon? How does this relate ...
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1answer
89 views

How does Diffie Hellman protocol work in Bitcoin Blockchain Transactions?

Greetings to all! Please explain how the Diffie-Hellman protocol works in Bitcoin? That is, in Blockchain Transactions, there is also a total number of "K" recipient and sender? "K" the recipient and ...
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0answers
10 views

Are compressed pairings used for Barreto-Naehrig curves in practice?

In 2009 Galbraith and Lin wrote the article "Computing Pairings Using x-Coordinates Only" https://link.springer.com/article/10.1007/s10623-008-9233-3, where they proposed to compute pairings on ...
2
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1answer
47 views

In ECC scalar multiplication, how do `add(Q, Q)` exceptions occur?

Consider some scalar multiplication algorithm for a prime order (Weierstrass) curve $E$ with order $\ell$. Bernstein and Lange's SafeCurves: Completeness page mentions: The problem is that the ...
7
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1answer
263 views

Proving that the least significant bit of an elliptic curve discrete logarithm is $0$

Suppose I have a secret value $a$ which maps to a public point on an elliptic curve $A = a \cdot G$, where $G$ is a generator of the elliptic curve of prime order $q$. Can I prove to someone that the ...
2
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1answer
44 views

Embedding POW in an EC public key

I have an application where it would be advantageous for an attacker to have to spend a long time generating public keys. To do this, I require that the hash of the public key be less than a certain ...
8
votes
2answers
521 views

Geometric interpretation of an Edwards curve

Addition on an elliptic curve in Weierstrass form (over the rationals) is typically depicted with the following figure: (Image CC SA 3.0 https://en.wikipedia.org/wiki/File:ECClines.svg) To add two ...
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1answer
62 views

How to compare the order of elements in cyclic groups?

In a cyclic group with randomly looking behavior like the one used in secp256k1, is there any known efficient algorithm to compare the order of two randomly given elements $P_1$ and $P_2$ and find out ...
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1answer
110 views

What is the point at infinity on secp256k1 and how to calculate it?

I hear that there should be a point at infinity on secp256k1. I wounder how to calculate it and what does it even mean. I tried to calculate it as $P_{inf}=P+(-P)$ but this gives different results for ...
4
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1answer
63 views

Does Elliptic Curve Integrated Encryption Scheme (ECIES) provide IND-CCA2 security?

I am looking for a faster alternative to RSA with OAEP as a IND-CCA2 public key scheme. Elliptic Curve Integrated Encryption Scheme might be a candidate, but I am not sure if it provides IND-CCA2 ...
7
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2answers
436 views

Should we use IANA groups 14 (MODP), 25, and 26 (ECP)?

By looking at SonicWall Knowledge Base article Key exchange (DH) Groups Supported - Site to Site VPN: It appears that our firewall supports DH group 25, and 26. Almost everywhere I've seen, they've ...
5
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1answer
122 views

Are EC public key values evenly distributed?

At my Day Job(tm) we've encountered a bug wherein if the leading digit of the X or Y value of a public key are zero, "shit happens" (this bug is in our code - I'm not suggesting there's some problem ...
1
vote
1answer
76 views

Could the reversibility of adding function be considered a weakness to secp256k1?

I have just started studying cryptography and secp256k1. I just wonder that adding two points can be easily reversible when the generator point is publicly known. I mean that if $Q=\operatorname{...