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Questions tagged [dsa]

The Digital Signature Algorithm (DSA) is a United States Federal Government standard or FIPS for digital signatures. It was proposed by the National Institute of Standards and Technology (NIST) in August 1991 for use in their Digital Signature Standard (DSS), specified in FIPS 186, adopted in 1993. A minor revision was issued in 1996 as FIPS 186-1. The standard was expanded further in 2000 as FIPS 186-2 and again in 2009 as FIPS 186-3.

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15 votes
2 answers
26k views

ECDSA Signature R|S to ASN1 DER Encoding question

I am trying to test my understanding on ECDSA Signature r|s to ASN.1 DER Encoding for NIST P-256. I have r|s and when I convert ...
1 vote
0 answers
60 views

Does unlimited signing oracle leak the private key?

I am writing a PC software that uses a type of USB dongle as licensing key. The dongle functions as a signing oracle and does nothing more: Given any message $M$, it first pads $M$ to $PadM$, then ...
1 vote
1 answer
93 views

RFC6979: Can deterministic ecdsa signature diverge with same key and message?

As I understands, RFC6979 uses deterministic K which is generated by HMAC-SHA256(private_key, message). In this way, I guess if same key with same message, ecdsa signature generated would be always ...
43 votes
3 answers
27k views

How does recovering the public key from an ECDSA signature work?

It is possible to recover the public key from an ECDSA signature values $(r,s)$? Please explain how this works.
1 vote
0 answers
87 views

Math of Hint usage in Dilithium

For Dilithium, I understand that $$\text{HighBits}(\mathbf{Ay}) = \text{HighBits}(\mathbf{Ay} - c\mathbf{s_2}) = \text{HighBits}(A_z - c\mathbf{t})$$ The first term of the equation is performed on the ...
1 vote
1 answer
92 views

Is it possible to break a DSA with k that increases statically?

I am currently studying cryptography. I came across this problem: I had an exercise that as a vulnerability had that k is generated every 10 seconds: ...
1 vote
0 answers
177 views

Need help with Cryptohack's ProSign 3 ECDSA problem [closed]

I'm trying to solve the CTF challenge called ProSign 3 at Cryptohack platform which involves exploiting an ECDSA signing service that allows us to sign a fixed message being padded with the time ... ...
4 votes
1 answer
238 views

Split a private key into shares and sign successively or separately

Assume I have a private key, priv_k, a public key pub_key and a message, msg, along with its ...
6 votes
2 answers
335 views

Blinding an ECDSA private key without learning the private key

I am looking at ways to blind an ECDSA signing key (and verification key respectively). Looking at proposed solutions like the IETF KBSS draft, and the IETF ARKG draft it seems that the ECDSA key ...
1 vote
0 answers
56 views

Single ecdsa signature valid for two different messages

I have been reading Flaws in Applying Proof Methodologies to Signature Schemes and ran into a bit I do not understand. In section 4.2 the authors describe a scheme where a malicious signer crafts a ...
2 votes
1 answer
86 views

Small subgroup attack when using a Schnorr group for DHKE

One uses a Schnorr group both for Schnorr signature (or DSA), and for Diffie-Hellman Key Exchange. They target 128-bit security, and choose prime $q$ that's 256-bit, prime $p=q\,r+1$ that's 3072-bit, ...
1 vote
1 answer
67 views

How should I map E'(Fp6) --> E'(Fp) starting from Bitcoin public key coordinates(x,y)?

Let $p$ be the prime number 115792089237316195423570985008687907853269984665640564039457584007908834671663 and let $E$ and $E'$ be the curve equations $$E(\mathbb ...
1 vote
2 answers
71 views

App for Secure delivery of the gray images using AES, DH, DSA - Help in implemeting the system structure

I have this uni project that I have to implement in code: "App for Secure delivery of the gray images, encryption-decryption with AES in OFB mode + secret key delivery using Merkle–Hellman ...
32 votes
2 answers
19k views

ECDSA Compressed public key point back to uncompressed public key point

From the ECDH demo here, if I generate a private key for Alice I can get _ P = 1175846487558108474218546536054752289210804601041 Which gives the following public ...
9 votes
1 answer
19k views

What is the recommended minimum key length for ECDSA signature

I want to identify the proportion of certificates that use unrecommend ECDSA key length for TLS certificates based on some data I collected. By looking at a standard like NIST for example, I find ...
3 votes
1 answer
499 views

What's the problem with ECDSA and SHA-3?

To quote Ilari on the CFRG mailing list: e.g. the vile mess that is ECDSA with SHA-3 I have some ideas what he might mean but I couldn't find the discussion so what is that mess?
3 votes
0 answers
211 views

Prove DSA signature scheme is EUF-CMA secure

I want to prove that the DSA signature scheme is EUF-CMA secure in the random oracle model, if the discrete logarithm problem is hard. I know it can be proved by the following two parts: Discrete ...
3 votes
0 answers
72 views

Is it fine to use ECDSA with edwards25519?

The elliptic.js library allows instantiating ECDSA with the edwards25519 curve. I've rarely seen this combination in the wild. ...
0 votes
0 answers
29 views

P256 signature verification was succeed with 2 public key [duplicate]

I tried to recover public key from P256 signature. With 2 recovery id ( 0, 1 ), signature makes 2 public key. And I tried to verify signature with public key and verification was succeed all of 2 keys....
1 vote
0 answers
63 views

Using Deterministic ECDSA (secp256k1) Signature as a Cipher Key in Symmetric Encryption

I'm exploring the security implications of utilizing a deterministic ECDSA signature as a cipher key for symmetric encryption and would appreciate insights from the community. Here's the setup I'm ...
2 votes
0 answers
57 views

threshold signature scheme that allows adding and removing members

Is there a threshold signature scheme (TSS) that a quorum in a group can sign, where members can dynamically join and leave, without changing the shared group public key? ECDSA, BLS, and Schnorr based ...
1 vote
0 answers
124 views

ECDSA: Can we use the private key for a different curve? [closed]

ECDSA can be instantiated with a variety of different elliptic curve groups. Two example curves are secp256k1 and edwards25519. ...
3 votes
1 answer
2k views

Can Montgomery ladder multiplication be used with secp256k1?

While reading about Elliptical Curves and ECDSA, I found a paper ECDSA Security in Bitcoin and Ethereum: a Research Survey by Hartwig Mayer. On page 6, the authors say: The curve secp256k1 does not ...
2 votes
2 answers
443 views

ECDSA-SHA256 HTTP Signature String Construction

I must verify an HTTP signature to guarantee the origin and integrity of a webhook data: https://www.blockcypher.com/dev/bitcoin/#webhook-signing This is their x509 PKIX encoded signing key's public ...
3 votes
1 answer
89 views

Why are there two Challenges in the DSA Identification Scheme?

Would either $\alpha$ or $r$ suffice as challenge? I am aware that the signature and verification were to adapt. However, what is the motivation behind using two challenges?
20 votes
2 answers
13k views

Difference between X25519 vs. Ed25519

I am reading https://en.wikipedia.org/wiki/Curve25519 and it states Also in 2018, RFC 8446 was published as the new Transport Layer Security v1.3 standard. It requires mandatory support for X25519, ...
1 vote
1 answer
123 views

Understanding the Communication Protocol of Apple HomeKey

I am currently analyzing the communication protocol of HomeKey. Here are two traces between the lock (reader) and the device (card). First set: ...
0 votes
0 answers
57 views

DSA using same k value, recover secret

I have two signatures $(r,s)$ and $(r,s')$. So the same $k$ is being used for generating the $r$ value. I know that this exposes a vulnerability such that I can recover the secret $x$. The first step ...
1 vote
1 answer
129 views

Working with Paillier and ECDSA - Order issue

I'm trying to implement two party computation for ECDSA signing using Paillier cryptosystem. But my problem is that the order of Paillier is different from the order of the curve (secp256k1 in my case)...
3 votes
2 answers
400 views

Security Level of DSA given parameters

So I'm trying to compare different digital signatures, and thus I stumbled upon a DSA algorithm. I'm using python's cryptography library, and it offers following values for L and N: L=1024,N=160 L=...
3 votes
0 answers
192 views

EC public key with leading zeros

Let us take example of secp256k1 curve. The current known public key with most leading zero (in x cordinate) is: ...
3 votes
1 answer
2k views

Why do we need additional secret value (k) in ECDSA?

Formula for calculating an ECDSA signature (r, s) is: s = k-1(z + qr) k - private key for a random point R z - hash of a message q - original private key r - x(R) I am interested in why do we need ...
6 votes
2 answers
2k views

Are curve secp256k1 ECDSA signatures distinguishable from random data?

Are the 64-byte curve secp256k1 ECDSA signatures distinguishable from random data? I.e. Given a random private key and random data, will there be patterns? Is there a proof or reasoning for this?
4 votes
1 answer
413 views

Does ECDSA leak information about the message hash?

ECDSA works by computing the hash of a message and then computing the signature for it. ECDSA uses the signature: $$s = k^{-1}(h + rp_{pr})\,\textrm{mod } n,$$ where $n$ is the order of the group, $k$ ...
1 vote
0 answers
61 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
38 views

Three ECDSA signatures sharing first component r, verifying against same message and public key?

For some common curve, can we exhibit three distinct ECDSA signatures $(r,s_1)$, $(r,s_2)$, $(r,s_3)$, a message $m$, and valid public key $Q$, such that the signatures verify? Can we also generate ...
1 vote
2 answers
197 views

Can ECDSA be broken if same nonce is used with the same message?

I have a scenario where $k_2 = -k_1$ while $z_1$ and $z_2$ are identical but the values $s_1$ and $s_2$ are different. So we have $r_1 = r_2$ and $z_1 = z_2$ but $s_1 \neq s_2$. Does this mean an ...
6 votes
4 answers
1k views

Why R value in signatures have to be 'calculated' values and not just a random numbers?

This document (page 27) says that: The only significant difference between ECDSA and DSA is in the generation of $r$. ECDSA $r = (kG)_x \bmod n$ and, DSA: $r=g^k \bmod p$ Why is it necessary to ...
3 votes
1 answer
126 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 & ...
0 votes
0 answers
47 views

Is this ECDSA's protection mechanism or something wrong with it?

Over the past few months, I have been reading and trying to understand how ECDSA works and how safe is it. So now something does not add up between its signature verification and generation. But maybe ...
0 votes
0 answers
56 views

Framework for manipulating digital signatures

for a research project, i am currently looking for a way to manipulate the digital signature of a HTTPS TLS message flow. More specifically, i am trying to create a working example for a malicious ...
2 votes
0 answers
135 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, ...
0 votes
0 answers
70 views

Same message different nonce but similarities in r value of the signatures(r,s)

I'm studying a case where when i sign a same message with the same private key and a different nonce, i sometimes get signatures (r,s) where r values share some similarities (same numbers at the same ...
36 votes
4 answers
13k views

Can ECDSA signatures be safely made "deterministic"?

Using the terminology of the ECDSA Wikipedia page, ECDSA (and DSA) signatures require a random k value for each signature which ensures that the signature is different each time even if the message ...
0 votes
0 answers
47 views

Practical deployments of ECC with cofactor of elliptic curves $4$ or $8$?

Are cofactor $4$ and $8$ ECC schemes widely used in practical deployments such as those in cryptocurrencies? Can you name some practical settings where there curves are used and cryptocurrencies where ...
2 votes
1 answer
271 views

Does RFC 6979 unconditionally prevent nonce-reuse attacks?

Is RFC 6979 guaranteed to prevent the reuse of nonces for different signed hashes?
13 votes
2 answers
17k views

Why OpenSSH prefers ECDSA nistp256 keys over -384 and -521, and those over Ed25519, for host key verification?

According to ssh_config(5), HostKeyAlgorithms “specifies the host key algorithms that the client wants to use in order of ...
1 vote
2 answers
68 views

In ECDSA over K256, Why R.x should be less than the subgroup order, not field order? But in BIP340 over K256, should be less than field order

I understand that R.x is a field element. I don't understand why in ECDSA verification ie. FIPS 186-5 section 6.4.2 step 1, we check whether r is less than subgroup order. If it has something to do ...
9 votes
2 answers
7k views

Complete Set of Test-Vectors for ECDSA secp256k1

Although there are several implementations of ECDSA secp256k1 public available over the internet (the most popular being OpenSSL), it seems that there are no complete set of test-vectors available. ...
0 votes
1 answer
81 views

Reason for two random numbers in DSA?

Why is the signature in DSA the way it is? I am referring to $r$ and $k$ in the Signing-Algorithm depicted below. Is it really necessary to have both, $r$ and $s$, or would it still be secure if only ...

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