Questions tagged [ed25519]
Ed25519 is an algorithm for producing digital signatures. The algorithm is based on Edwards curves introduced by Bernstein et al. (2007) and named after mathematician Harold M. Edwards.
209 questions
2
votes
0
answers
58
views
How is ed25519 sc_reduce derived?
The supercop implementation of ed25519 features a function called sc_reduce that computes the modular operation a % l for a fixed big number l.
Here you can see the implementation:
https://github.com/...
- 121
2
votes
0
answers
48
views
Does the supposed domain separation make it safe to reuse Ed25519 public key for Curve25519 key establishment?
The "Similar Questions" section under my title suggest several similar questions on this, but none touched on that explicitly.
Because Montgomery curves have birationally equivalent Edwards ...
- 9,795
1
vote
0
answers
44
views
Is it possible to encrypt a message using only the recipient's Ed25519 public key?
Suppose:
Alice knows the Ed25519 public key of Bob
Bob is using his Ed25519 private key / seed in the usual way for digital signatures
Clearly, Alice can verify messages signed by Bob.
Is there any ...
- 141
2
votes
1
answer
84
views
What Digital Signature Methods are Suitable for Microcontrollers?
Given the constraints in terms of processing power, memory, and energy, what digital signature schemes are commonly used and efficient for Microcontrollers? I have come across RSA with low public ...
- 101
1
vote
0
answers
62
views
Is it possible to compute the X25519 scalar multiplication of the SSH key exchange using the ED25519 sliding window implementation?
There are many different ED25519/Curve25519/X25519 implementations around. I focus on two of them:
https://github.com/jedisct1/libsodium
https://github.com/floodyberry/ed25519-donna
The libsodium ...
- 156
0
votes
2
answers
105
views
Public proven methods to generate SSH key from pass phrase?
Do we have something proven APPS for generate ssh key from some words?
I mean private key(without reason wich type rsa or eleptic curves) generated deterministic from seed
I found this fork of ssh-...
- 3
0
votes
0
answers
98
views
ed25519: Scalar multiplication guaranteed to land in prime order subgroup?
ed25519 is defined over curve edwards25519 which has a large prime order subgroup and a small subgroup of order 8.
During key generation, bit clamping is used to ...
- 697
0
votes
1
answer
113
views
Threshold ed25519: How to export keys?
Consider ed25519 signing (RFC 8032).
There, the private key is a 32-byte random value, and for signature generation, the 32-byte private key is first hashed and then the secret scalar and nonce are ...
- 697
3
votes
1
answer
150
views
EdDSA signing modification
I've got a question regarding the signing algorithm on elliptic curves (EdDSA). In ed25519 signature scheme there is no nonce $k$, instead every message has its own different hash. From what I know ...
- 31
1
vote
1
answer
84
views
Radix-2^51 arithmetic of edwards25519
The Golang implementation of edwards25519 (https://tip.golang.org/src/crypto/internal/edwards25519/field/fe.go) uses radix-251 representation. The description in section 3.2 in https://dl.acm.org/doi/...
- 35
1
vote
2
answers
268
views
Challenge with curve ed25519
Recently a friend of mine showed me a "puzzle" he created with curve ed25519
It is based on adding and multiplying points on the curve
You supply three arguments to the program
...
- 11
0
votes
0
answers
65
views
Ed25519 and sealed boxes libsodium
Accidentally used ed25519 public key to create libsoidum_sealed_box. Is there any way to decrypt the data if the private key ed25519 is known?
1
vote
1
answer
302
views
Is it safe to derive Ed25519 and Kyber private keys from the same seed?
I am designing a Hybrid Key exchange library using x25519 and Kyber, and the scheme I have in mind is as follows:
Alice sending a file/message to Bob:
...
- 59
3
votes
1
answer
683
views
Current Digital Signature Standards as of late 2023
Is my summary understanding of current (classical) Digital signature standards essentially correct? I may be totally wrong.
DSA is no longer to be used for new signature generation just for checking ...
- 23.7k
0
votes
0
answers
109
views
A matching X25519 public from non-clamped Ed25519-public and Ed25519-secret
Given an Ed25519 key pair, can you think of any way to get to the same X25519 public key from the Ed25519 secret as from the non-clamped(!) Ed25519 public key?
...
2
votes
1
answer
92
views
What would be the security consequences of replacing $H(R, A, M)$ with $H(R, M)$ in EdDSA?
The question is mainly stated in the title. We don't consider any other changes to the scheme except for the following:
We replace $S = H(R,A,M) \cdot a + r$ with $S = H(R,M) \cdot a + r$.
My thoughts ...
- 992
1
vote
0
answers
64
views
Curious behavior of EVP_DigestSign for DKIM
Difficulties porting code to OpenSSL 3 may raise some doubts on digest signing. Before version 3 came, digest signing was the only way to use ED25519. On version 3, RSA_sign() being deprecated, I ...
- 111
9
votes
1
answer
903
views
Why does Ed25519 use a twisted Edwards curve rather than a regular Edwards curve?
I'm trying to understand benefits of using Twisted Edwards curve over regular Edwards curve. I'm aware of some properties of Twisted Edwards curve that regular Edwards curve missing like isomorphism ...
- 491
1
vote
0
answers
175
views
Edwards curve ed25519 puzzle [duplicate]
Recently a friend of mine showed me a "puzzle" he created with edwards curve ed25519
It is based on adding and multiplying points on the curve
You supply four arguments to the program
The '...
- 11
0
votes
0
answers
38
views
Academic papers for the pros and cons of password based system and digital signature with challenge and response system
I don't really know what should be the correct title for this and the community can correct it after reading.
I was the author of PKDSA (Searchable on github).
I have the idea to do it because I feel ...
- 159
0
votes
0
answers
92
views
Digital signature with challenge and respond with PQC
Can ECDSA signature signing and verification process replaces password hashed based login system?
The title of this question won't be exactly right.
This is a question that I asked long time ago. I ...
- 159
5
votes
1
answer
286
views
RFCs & IANA specs about Ed25519 inaccurate?
While designing a crypto system based on existing standards and specifications i find myself questioning some of the accuracy in the current RFC-8037 and IANA specs around Edwards curves, 25519 and ...
- 153
10
votes
1
answer
1k
views
Why Ed25519 encodes y-coordinates rather than x-coordinates
As stated in RFC8032 and FIPS 186-5, Ed25519 signatures uses the following encoding method:
A curve point (x,y), with coordinates in the range 0 <= x,y < p, is
coded as follows. First, encode ...
- 2,903
1
vote
0
answers
48
views
Standard vs. specific mappings in SP800-186 for code reuse between different curve models
The final SP800-186 outlines mappings between Twisted Edwards and Montgomery curves, and between Montgomery and Weierstrass curves.
These mappings are defined in Appendix B. Relationships Between ...
- 346
4
votes
1
answer
430
views
Breaking Ed25519 Discrete Logarithm with Degenerate Curve Attack
Following this question ed25519 attacks and also this paper on degenerate curve attacks https://eprint.iacr.org/2015/1233.pdf, I tried to implement my own attack: Given a point (0, y) and a scalar (k),...
- 77
9
votes
2
answers
2k
views
How many valid X25519 private keys are there?
According to the Curve25519 website:
Computing secret keys. Inside your program, to generate a 32-byte Curve25519 secret key, start by generating 32 secret random bytes from a cryptographically safe ...
- 257
5
votes
2
answers
899
views
Deriving private keys from a signature/HSM
I have access to an HSM that can sign messages but doesn't have a way to expose the private key. The signatures are deterministic (RFC 6979). Another application only works with ed25519 signatures ...
- 53
2
votes
1
answer
63
views
Which service provider can create (claimable) accounts for managing Ed25519 keypairs (zero-knowledge fashion) by email
The title is a mouthful, allow me to explain my situation.
I have a SaaS with many users.
When new users join the platform, I want to create a cryptographic keypair for them (Ed25519).
But I don't ...
- 21
6
votes
2
answers
648
views
"Cropping" the resulting shared secret from ECDH
I'm deriving a shared secret using ECDH with Ed25519 keys. According to the specification (page 5), the shared secret then can be any valid Curve25519 public key, i.e. any valid 32 bytes. My ...
user80785
3
votes
1
answer
287
views
Details about blind signature on ed25519
Recently, I started looking up for details about implementing a blind signature on ed25519 cryptographic. I saw this article https://stan.bar/blindsig/ by Stanislaw Baranski about it.
In the first ...
- 33
1
vote
1
answer
445
views
Why are hashing private key in Ed22519 key generation and later the modifications required?
In EdDSA with Ed25519 the algorithm of public key computing is following:
h = hash (privateKey)
h[0] &= 0xF8
h[31] &= 0x7F
h[31] |= 0x40
publicKey = h * B
...
- 151
4
votes
1
answer
284
views
How are the unified addition formulae in extended twisted Edwards coordinates derived from the affine addition formulae?
I am trying to understand point addition in RFC8032 section 5.1.4, which references the paper "Twisted Edwards Curves Revisited" (https://eprint.iacr.org/2008/522.pdf) to describe the quick ...
3
votes
1
answer
884
views
Find Ed25519 Y Coordinate from X Coordinate
Are there any available formulas to determine a $Y$ coordinate given only an $X$ for the Ed25519 curve? The closest thing I've come to find is the recover_x(y, sign)...
- 77
2
votes
1
answer
239
views
In Ed25519, why not make both batch & unbatched verification follow the cofactored verification approach rather than unbatched using cofactorless?
Ed25519 uses a composite order Elliptic Curve (with a cofactor $8$) The algorithm however in the prime order subgroup of the main group. The signing operation should be using a generator/Base Point ...
- 2,316
3
votes
2
answers
172
views
Ed25519 - Is there a reason to not trust the signer - i.e. can there be a dishonest signer?
Ed25519 uses a composite order Elliptic Curve but works in the prime order subgroup of the main group. The signing operation should be using a generator/Base Point from the prime order subgroup.
This ...
- 2,316
5
votes
3
answers
804
views
When working in a subgroup of EC in EdDSA (especially Ed255190), how is it OK to use operations different from that of the main group?
Ed25519 uses a composite order Elliptic Curve but works in the prime order subgroup of the main group. As per group theory, the subgroups use the group operation.
However, as per this, Ed25519 ...
- 2,316
0
votes
0
answers
218
views
Fast methods for adding the basepoint to an elliptic curve point?
Are there any clever (fast) methods for adding the basepoint (generator) to an arbitrary point on elliptic curve, finally ending in affine coordinates?
I.e. if G is ...
- 1
1
vote
1
answer
649
views
Why Can't I Use an Nacl Sign Keypair for Encrypt and Decrypt Operations?
I'm aware that the difference between the NaCL sign keys vs the box keys is that the secret key that comes from the NaCL box keypair is the ...
- 113
0
votes
0
answers
77
views
Check if pubkey belongs to twisted Edwards25519
I want to check if some pubkey belongs to twisted edwards25519 (I guess this is used for ed25519 ?) The problem is that I have in theory some valid pubkeys like:
...
- 103
2
votes
1
answer
3k
views
Can OpenSSL sign an ED25519 certificate with ECDSA-with-SHA256?
We are trying to generate some self-signed certificates to test our cybersecurity firmware before switching to a "real" CA-signed chain of trust. The specification we are coding to mandates ...
- 121
0
votes
0
answers
144
views
Using ed22519 signature as entropy
I am developing an application in which all application state is entirely public. Each user of the application is equipped with their own ed22519 keypair, and the application can only ask users for ...
4
votes
2
answers
416
views
Isomorphism of Curve25519 and Ed25519?
According to this page, Curve25519 and Ed25519 are not isomorphic, because the birational equivalence equation has singularities:
What does "birational equivalence" mean in a cryptographic ...
- 2,625
2
votes
1
answer
291
views
What is a masked secret key in the conxt of Ed25519?
The documentation for Ed25519-dalek states the following for Secretkey:
The caller is responsible for ensuring that the bytes represent a masked secret key.
https://docs.rs/ed25519-dalek/0.3.2/...
- 131
1
vote
0
answers
75
views
Differing result between doubling and addition in extended twisted Edwards coordinates [closed]
While coding for Edwards curve, I noticed that, the addition formula and the doubling formula return what seems to be different result.
I took the adding and doubling formula from both RFC-8032 and ...
- 9,795
2
votes
1
answer
551
views
Test vectors (points) for Ed25519
I am trying to verify an Ed25519 implementation, but I can't find any test vectors for the curve points. All test vectors focus directly on signature constructions (EdDSA).
I tried to use https://...
- 1,745
3
votes
1
answer
4k
views
Generating and validating a signature with ED25519 expanded private key
I am building a encrypted messaging app over tor network and currently I'm struggling on using tor generated ed25519 private key to sign and verify any message.
Below piece of code works with a 32 ...
- 31
1
vote
0
answers
90
views
Collision-resistant single-pass EdDSA?
Is there any reason why collision resistant variants of ed25519 that use a single-pass aren't used instead? For example:
$n = h(noncekey \| m)$
$h(R \| pub \| n)$ instead of $h(R \| pub \| m)$
or ...
- 87
3
votes
1
answer
1k
views
Ed25519 to X25519 transportation
Using
montgomeryX = (edwardsY + 1)*inverse(1 - edwardsY) mod p
it is possible to transport an Edwards curve point (Ed25519 ...
- 65
3
votes
1
answer
762
views
ed25519 attacks
I try to understand invalid curve attack and small subgroup attack.
The lower 3 bits of a ed25519 private key are cleared to be a multiple by 8.
So an attacker is unable to gain any information using ...
- 65
1
vote
0
answers
47
views
Is partial computation of an Ed25519 Diffie-Hellman shared secret possible?
Let's say we're using the Ed25519 curve, and we're computing a Diffie-Hellman shared secret EC point $S$ by scalar multiplication of scalar $a$ with EC point $B$.
Is there any way of partially ...
- 4,790