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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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20
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2answers
4k views

Using same keypair for Diffie-Hellman and signing

Are there any security risks using a single key-pair for both key-exchange and signing? I'm mainly interested in using Curve25519 for key-exchange and Ed25519 for signing. But similar combinations, ...
32
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2answers
11k 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.
26
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1answer
11k 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 ...
13
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1answer
2k views

How does the “biased-$k$ attack” on (EC)DSA work?

I recently stumbled across Thomas Pornin's old answer about deterministic (EC)DSA again. There he states the following: Note that $k$ must be generated uniformly in the $[1, q-1]$ range (where $q$...
11
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1answer
682 views

(EC)DSA signature without hashing, or with offloaded hash?

In (EC)DSA as per FIPS 186-4, the message to sign is first hashed. Imagine that we skip this hashing stage, instead put the message where the hash was, and constrain the size of message $h$ to the ...
24
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3answers
6k 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 ...
4
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1answer
446 views

How should ECDSA handle the null hash?

In ECDSA, assume your public key is $Q=(x,y)$, then when performing the verification of any message leading to a null hash value (that is $H(M)=0$), the signature $(r,s)=(x,x)$ would always lead to a ...
7
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1answer
590 views

Is it possible to weaken a bitcoin private key by “using” it elsewhere?

What are the increased possibilities (if any) of being able to crack a private key given the following: The associated bitcoin (ECDSA Secp256k1-based) public key is known. The private key has been ...
1
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1answer
561 views

Does “hash than sign paradigm” apply to ECDSA cryptography?

From wikipedia https://en.wikipedia.org/wiki/Digital_signature#How_they_work and other articles I see that: "There are several reasons to sign such a hash (or message digest) instead of the whole ...
44
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2answers
63k views

Signatures: RSA compared to ECDSA

I'm signing very small messages using RSA, and the signature and public key are added to every message, which requires a lot of space compared to the actual content. I'm considering switching to ...
9
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1answer
20k views

How can I convert a DER ECDSA signature to ASN.1?

I having trouble verifying an ECDSA signature signed using client side javascript with Java/BouncyCastle. The javascript signing function source: ...
14
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2answers
687 views

What is the intuition for ECDSA?

I understand DH and ElGamal and RSA encryption/signatures. But when I look at ECDSA (or plain DSA), it seems like the formulas are just pulled out of thin air. I can verify that the algebra used in ...
9
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2answers
6k views

Are there any Secp256k1 ECDSA test examples available?

Are there any available test cases for testing elliptic curves like secp256k1 (Korblitz curves from http://www.secg.org/collateral/sec2_final.pdf)? For curves like P192 there are for example those ...
21
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1answer
8k views

ECDSA, EdDSA and ed25519 relationship / compatibility

I'm trying to understand the relationship between those three signature schemes (ECDSA, EdDSA and ed25519) and mainly, to what degree are they mutually compatible in the sense of key pair derivation, ...
7
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1answer
1k views

Elliptic curve cryptography related key attacks [closed]

This question is an extension of Families of public/private keys in elliptic curve cryptography As described above, bitcoin "type 2" deterministic wallets use a root private/public key pair, where ...
7
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2answers
1k views

How is the x coordinate of a “point at infinity” encoded in a Secp256k1 signature?

I'm testing an implementation of Bitcoin, which uses the curve Secp256k1 for ECDSA, and I want to see how it handles the point at infinity ($0$) if present in a signature. For example, r could be the ...
5
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1answer
2k views

ECDSA: How to retrieve a non-random k

I have a question regarding the random $k$ number of ECDSA encryption. As far as I know, it is possible to retrieve $k$ (and thus the private key) from two signed messages if both used the same $k$. ...
2
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1answer
949 views

Can I shorten the large ECDSA public key output file from OpenSSL?

I am working in a very bandwidth restricted environment where I from time to time have the need to distribute public keys. The distribution happens in bit format, so there is no need for encoding, at ...
24
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1answer
17k views

How strong is the ECDSA algorithm?

Some cryptographic algorithms are as strong as the size of their key is, while other have some weaknesses that limit their strength (such as SHA-1). How strong is the ECDSA algorithm, and does that ...
22
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2answers
9k views

HMAC vs ECDSA for JWT

I will be implementing JSON web tokens into my website and have a question about implementing them. I have a choice of using two algorithms, HMAC-SHA256 and ECDSA-SHA256. I have used HMAC-SHA256 in ...
10
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1answer
1k views

RFC 6979 - Why not simply hash the message & the private key for deterministic ECDSA?

Why go through the trouble of using the HMAC_DRBG process, instead of simply hashing [message | private key] to calculate $k$ for deterministic ECDSA? If the ...
14
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2answers
3k views

Can one reduce the size of ECDSA-like signatures?

Using $n$-bit ECDSA, a signature has a size of $2·n$. It is possible to recover the public key from this signature, which shows that there is a publicly visible redundancy in the signature. Is ...
13
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2answers
678 views

Is it safe to reuse a ECDSA nonce for two signatures if the public keys are different?

We denote the s value of an ECDSA signature $(r, s)$ on a message $m$ as: $s=\frac{H(m)+xr}{k}$ Assume two ECDSA signatures sharing the same nonce $(r, s_1) , (r, s_2)$ on two messages $m_1, m_2$, ...
10
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3answers
17k views

Using ECDSA keys for encryption

I know that ECDSA is used for signature only, but I wonder if I can use the public/private Elliptic Curve keys for encryption too. I have ECDSA SSH public keys and I wonder if I can use them to ...
9
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1answer
4k views

ECDSA vs RSA: Performance on Android platform and surprising results

For our privacy-preserving protocol, an encrypted channel is established. In order to protect our system from man-in-the-middle attacks, signature-based approach is used. After we've implemented it ...
2
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1answer
2k views

Attack on DSA with signatures made with k, k+1, k+2

For homework, I'm asked to find the private key, $x$, in a DSA digital signature scheme. In the particular instance, we are given the parameters $p$, $q$ and $g$, the public key $g^x$, 3 messages $(...
9
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1answer
1k views

Simple digital signature example that one could compute without a computer?

I am working on a document to explain Bitcoin to students. But I am having a hard time translating the principle described in §2 of the Bitcoin whitepaper in layman's terms. There is a great question ...
6
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2answers
133 views

Why ECDSA has its form?

According to Wikipedia, if Alice wants to sign some message, she computes $s = k^{-1} (z + r d_A)$ then sends $(r, s)$ to Bob. I don't understand why they use this particular formula $s = k^{-1} (z + ...
9
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1answer
478 views

Why use $(r,s)$ instead of $(r,s^{-1})$ as DSA signature?

A DSA signature consists of two scalars $(r,s)$. When signing $s$ is generated as: $s=k^{-1}(H(m)+xr) \mod q$ The signature is $(r,s)$ When verifying $s$ is only used to compute $w = s^{-1}$. So ...
6
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1answer
1k views

Threshold Signatures for RSA and DSA

I have a few questions relating to threshold signatures: a scheme where $n$ participants hold a key share and any $t$ of them can conduct a protocol using their shares that results in a valid RSA or ...
6
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1answer
5k views

How do RSA and ECDSA differ in signing performance?

Signature algorithms with elliptic curves have smaller output sizes compared to RSA for the same level of security. What about the processing time to generate a signature ? I've seen figures giving ...
6
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1answer
470 views

preferred method for generating k for DSA / ECDSA

FIPS 186-4, sections B.2.1 and B.2.2, discuss two different methods for generating k for DSA / ECDSA. Unless I'm mistaken RFC 6979 discusses another method utilizing HMAC_DRBG. So what method is the ...
5
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1answer
1k views

In ECDSA, how many field operations are used for signature verification?

I am wondering about the computational cost of ECDSA signature verification, in term of multiplications in the base field; and, as an aside, in term of (much cheaper) additions. To make things ...
4
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2answers
2k views

Is there any reason to use RSA or DSA when we have ECC?

I am having trouble coming up with a use case for RSA or DSA. It appears that ECC is better in every way. Is this true? I am looking for cases where RSA/DSA is superior to ECC, not where it is used ...
4
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1answer
6k 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 ...
3
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2answers
2k views

Are ECDSA keys and RSA keys interchangeable?

Is it possible to use an ES512 key pair for RS512 signatures? Is it possible to use an RS512 key pair for ES512 signatures? I've also posted an issue in the NodeJS jwa package. I created a key pair ...
2
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1answer
156 views

Universal forgery based on mathematical problem

It is known that DSA admits universal forgery under assumption that the Attacker can solve the equation $x\equiv R^x\pmod p.$ Are there any other protocols admitting universal forgery based on non-...
0
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2answers
359 views

DSA with composite p

One of the basic requirements of DSA is to choose some prime $p$ of certain bit length. The security then lies in the intractability of solving $y = g^x \pmod{p}$ for $x$. Is there any “easy” way to ...
9
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1answer
1k views

Performance of ECDSA, ECKCDSA and ECGDSA

It is proven that ECDSA algorithms are faster in key and signature generation compared to RSA. In addition, the signatures are much shorter. However, I would like to know the performance difference ...
4
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0answers
189 views

What public-key encryption protocol can use the same key pair as ECDSA?

Assume we wanted to use the same ECDSA public/private key pair (drawn for standard ECC parameters, perhaps P-256) for both its intended use (public-key signature), and for public-key encryption; this ...
3
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1answer
504 views

How bad is it to use the identity function as hash for ECDSA?

I was recently asked whether a certain library supports the ECDSAwithNone Signature algorithm. Clearly this would mean ECDSA with the identity function as the hash function. I know this is a really ...
3
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1answer
500 views

Is it safe to use same private key in two or more EC signature algorithms?

Given two (or more) algorithms: ed25519 private key is random blob of 32 bytes public key is encoded point on Edwards 25519 curve. ECDSA with secp256k1 private key is random blob of 32 bytes ...
3
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1answer
115 views

Appending ECDSA signature to a message

I need to authenticate a message sent to an embedded device (which limits my options in terms of just using an existing convention). I can run ECDH/ECDSA on the device and can use SHA-256 as a hash ...
3
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1answer
2k views

Shouldn't a signature using ECDSA be exactly 96 bytes, not 102 or 103?

Attempting to use openssl to create a signature is confusing on several levels: If I'm using it to sign a hash that I've already created (HMAC-SHA-384-192, specifically), a. why must I specify ...
2
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2answers
368 views

ECIES with ECDSA

I understand how ECIES work. I have a structure of message [alice`s ephemeral public key, MAC tag, ciphertext] I do not understand what I shoud do if I want to ...
2
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1answer
2k views

Where can I find Secp256k1 ECDSA test vectors?

I`m currently implementing an ECDSA library based on curves like secp256k1. I would like to test it using some test vectors, like http://csrc.nist.gov/groups/STM/cavp/documents/dss/ecdsatestvectors....
2
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0answers
654 views

Elliptic Curve based blind signature implementation [closed]

I want to use Elliptic Curve based blind signature scheme for my research. There is no proper implementation of ECC-based blind signatures. Can someone describe to me which things I need to follow ...
2
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1answer
351 views

Verifying multiplicative inverse on a prime field in NIST's ECDSA_Prime.pdf

I am trying to learn about the Elliptic Curve Digital Signature Algorithm (ECDSA) by verifying the results in some example calculations. I found a PDF of example ECDSA calculations from NIST here: ...
2
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1answer
332 views

What is the difference between: ecdsap, ecdsak, and ecdsab in the output of “openssl speed”? What do the letters P/K/B refer to?

openssl speed tests the speed of different protocols on your computer: ...
1
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3answers
134 views

Digital Signature Algorithm for large files - bottle-necked by hash function?

I am new to studying digital signatures like ECDSA and EdDSA, and was curious about something. Lets say hypothetically I want to create a digital signatures of millions of files, with a total size of ...