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.

Filter by
Sorted by
Tagged with
6
votes
1answer
252 views

Elliptic Curve Cryptography - When to use p and when to use n

Im currently playing around with ECC, in particular the ECDSA scheme on a brainpool P256R1 curve. While implementing the signature verification function, I've stumbled upon a few problems. So far I'...
1
vote
1answer
95 views

Hybrid authenticated protocol

Let's suppose that two entities, A and B, are establishing a secure channel and then require a mutual authentication. A has only a RSA key pair and B has an ECDSA key pair. Both of them trust the ...
0
votes
1answer
704 views

In ECDSA, without knowing private key and any signature one can sign random garbage (from the Cryptography list)

Taken from the Cryptography mailing list. It is claimed that in ECDSA, without knowing the private key and any message signed with it, one can sign: "random garbage" (there is some complicated ...
0
votes
1answer
209 views

Signature operations may leak the private key; signature verification should be safe?

What does this warning mean: Signature operations may leak the private key. Signature verification should be safe. A haskell cryto library displays the quoted warning above (see Crypto.PubKey.ECC....
0
votes
1answer
116 views

Sign + ETM in ECIES

Using ECIES in a file encryption protocol, I need to authenticate the sender, so I'm using ECDSA, and I'm wondering if signing the ephemeral public key(needed by receiver to derive the shared ...
6
votes
1answer
469 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 ...
2
votes
1answer
531 views

How to sign different messages using deterministic ECDSA?

The elliptic JavaScript library implements a .sign function which seems to give the same result when signing the same message. That means the ...
7
votes
1answer
164 views

How many unique elements are generated by a variation on the equation in DSA for r?

How many unique elements are generated from the following equation? $$i = (g^x \bmod p) \bmod n $$ where: $g$ has order $q$ $q$ and $p$ are prime numbers $q\mathop{|}p-1$ $n$ is integer number more ...
1
vote
1answer
388 views

DH Key exchange attack: bad choice of g

In the group $\mathbb{F}_p^*$, Bob reads Alice's parameters as $p=234917$ and $g=281$ and uses a secret key $b < 400$ such that $h_b = g^b = 92646$. Note that $p-1 = 2^2\cdot 11\cdot19\cdot281$ $...
2
votes
1answer
965 views

ECDSA pubkey recovery issue

I try to recover public key from the given message $m$ and pair $(r, s)$ using curve that satisfies standard RFC7091. I am using algorithm from one of secp256k1 implementation but it seems that not ...
6
votes
2answers
3k 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. ...
1
vote
3answers
748 views

Which hash function is used for signatures ssh-rsa and ssh-dss?

I'm building a fuse client for ssh/sftp. I write the required ssh and sftp functions myself. Now I read in RFC4253 that before signing the data to sign is default hashed. In RFC4253 8. "Diffie-Hellman ...
2
votes
1answer
564 views

Calculating random number in ECDSA based on private key and signature

In ECDSA (Elliptic Curve Digital Signature Algorithm) we use a random number k in the signature process. Signature in ECDSA is: $$ (x_1,y_1) = k * G $$ $$r = x_1 \...
5
votes
3answers
440 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 ...
1
vote
1answer
219 views

Finding public key out of ECDSA certificate

I got an ECDSA certificate and now I'm trying to find out the public key. I'm not very familiar with this topic, so I hope you bear my (maybe silly question). The reason I'm doing this is, because my ...
3
votes
1answer
323 views

How do I generate a challenge for elliptic curve signing using NIST standards?

Basically, NIST FIPS 186-4 describes a standard for generating some message that will be signed by an elliptic curve private key. However, I'm having difficulty interpreting how this message should ...
3
votes
1answer
218 views

Why does FIPS 186-4 seem to have an excessively complex q generation?

So in DSA you have two primes - p and q. q is N bits long (let's assume 160 bits) and p is L bits long (let's assume 1024 bits). Here's what FIPS 186-4 says about generating the q parameter for DSA: ...
2
votes
1answer
229 views

Time efficiency of Bitcoin Multi-signature Vs. threshold signature

I read this paper (Securing Bitcoin wallets via a new DSA/ECDSA threshold signature scheme) that illustrated that threshold signature is the best solution to avoid single point of failure but I think ...
3
votes
1answer
973 views

When would I need DSA as opposed to RSA for digital signature?

The digital signature algorithm encrypts a hash using the senders private key and the receiver's public key. This multiple encryptions is a pretty expensive process since public key encryption is so ...
1
vote
1answer
269 views

Getting a key size of DSA/Elgamal certificate

I've tried to get a public key size of DSA/Elgamal PGP certificate. Using the Cleopatra I find out that there is actually two public keys - one with DSA with key ...
1
vote
0answers
834 views

Diffie-Hellman combined with DSA/RSA

we have learned Diffie-Hellman, RSA and DSA (Digital Signature Algorithm) in university. Because DH is vulnerable of Man-in-the-Middle we had the task to program the DH combined with RSA to protect ...
6
votes
1answer
12k views

Can a server's ECDSA fingerprint be spoofed during SSH?

I have read somewhere that Servers which have SSH access for users in the public can have their public key posted publicly (e.g., on a website), so that people who access such a server using SSH can ...
1
vote
1answer
2k views

ECDSA non random k - Retrieve private key [closed]

At the moment I'm playing around with ECDSA. I know that I can retrieve the private key if the same K is used to sign two messages. I tried to use this script: Ruby Script to crack the private key. ...
5
votes
1answer
521 views

ECDSA key recovery - floating point values

I'm currently attempting to recover an ECDSA key. I have $m$, $m'$ and signatures $(r, s)$, $(r', s')$, and I know that $k$ is constant, the curve is NIST P-192 and the hash function of the. As such,...
2
votes
1answer
145 views

Why is DSA falling out of favor?

Windows abandoned DSA rather than extend it to support > 1024 bits; but otherwise I cannot find a reason why DSA would be less desirable. I see in SSH the disabling it by default with a completely ...
2
votes
1answer
751 views

Why does DSA require that a new $k$ be chosen and the algorithm restarted if $s=0$?

DSA is an algorithm used to generate a digital signature, which consists of a pair of values $(r,s)$. The algorithm computes $r$ first and then $s$. However, if we calculate $s=0$, it says to restart ...
0
votes
2answers
121 views

Stripping off message authentication or signature

If attackers can strip off RSA / EC / -DSA digital signature and conduct CCA on AES-CTR or CBC payload, why can't they do the same for AES-GCM?
8
votes
0answers
117 views

Software timing attack using Kocher method

What's the minimum number of random sample points needed in Kocher's timing attack, so that we can determine enough valid measurements of $A_{i,r}$ and $D_{i,r}$? I'm working from this paper: Volker ...
1
vote
1answer
613 views

Does OpenSSL apply ASN1 encoding to the hash before signing using ECDSA?

I read on stack overflow that OpenSSL performs ASN1 encoding to the hash before signing it for, for ECDSA. In other words, OpenSSL performs the following steps when for an Elliptic curve key ...
14
votes
2answers
682 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 ...
1
vote
1answer
552 views

Better security than SHA1 for signature?

An application that I maintain uses Sparkle Update to update itself. I expect attacks from high level attackers (China, USA's NSA, etc.) and have some questions about how secure the cryptography ...
3
votes
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 ...
4
votes
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 ...
0
votes
1answer
558 views

Comparison Affine Coordinates and Projective Coordinates Addition in Excel

Kurve : EC : $y^2=x^3 + x + 1$ Generator:$(1,7)$ $p=23$ Result in Affine use Excel: $P=(1,7)$, $Q=(7,11) \implies P+Q=(18,20)$ Result in Projective use Excel: $P=(1:7:1), Q=(7:11:1) \implies P+Q=(15:...
0
votes
1answer
746 views

SHA1 collisions and the impact for ECDSA signatures

What will it mean for ECDSA using SHA1 when we have practical attacks breaking the collision resistance property of SHA1? [UPDATE] Added a bit more details to be clear. If $(r,s)$ is the ECDSA ...
5
votes
1answer
7k views

Should I use RSA encryption since RSA is said to be broken by NSA?

I am developing a simple web app that uses asymmetric encryption, but I am not sure whether to chose RSA for the reasons mentioned above. What are your suggestions? Also if I decided to go with RSA ...
4
votes
2answers
176 views

Are low security curves for ECDSA not supported?

I am working in a very bandwidth restricted environment, and we are looking to implement ECDSA digital signatures. Although they are no longer recommended, we might be looking to use curves that are ...
0
votes
0answers
35 views

Are the ECDSA public keys of a stable/fixed length relative to curve size? [duplicate]

I am working in an environment with strict bandwidth requirements, and we need predictable bit lengths of the stuff we send. We need to broadcast ECDSA public keys, and we are using OpenSSL to ...
2
votes
1answer
944 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 ...
9
votes
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 ...
2
votes
0answers
174 views

Cost of attack on DSA with attack on DLP

Are there any (recent) estimates of cost of attack on DSA by solving the discrete logarithm? I'm especially interested in attacks that use Pollard's rho algorithm. Are there any optimized ...
0
votes
1answer
225 views

Why is it that in DSA, the order of the subgroup, $q$, is chosen such that it divides $p - 1$?

Consider the DSA key generation: A large prime $p$ is chosen; A smaller modulus $q$ is chosen such that $p - 1$ is a multiple of $q$; A generator $g$ s.t. $\operatorname{ord}_p(g) = q$ is chosen. My ...
1
vote
1answer
97 views

What happens when domain parameter $q$ in DSA is not prime number

Suppose that attacker creates domain parameters $(p,q,g)$ where $q$ is not prime number (but $q$ still divides $p-1$) and that signer generates new key pair using these domain parameters. How exactly ...
1
vote
0answers
281 views

How to check the signature without the predetermined function in ECDSA from openssl? [closed]

I'm developing a client for a two-factor authentication in Qt/C++ under openSUSE 13.2, 64bit. I've got the FIDO U2F Security Key from yubico/fido. I'm using the classes from openssl, in particular <...
6
votes
1answer
283 views

Is there any reason not to use EdDSA with Weierstrass curves?

I'm volunterely working for a crypto library and we're planning on adding Curve25519 support (finally). At the same point I had the idea of adding support for EdDSA in the same run. Our library is ...
22
votes
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 ...
2
votes
1answer
2k views

RSA vs ECDSA/ECDH

So we've been using RSA for a while now. I wonder, is it still secure? I'm wondering whether surveillance agencies can at this point read traffic encrypted with say, TLS_ECDH_RSA_WITH_AES_128_GCM? ...
2
votes
1answer
135 views

Is there a single-use signature scheme, where a second use of the private key discloses it to the world?

With ECDSA (and possibly DSA too) I'm aware that if the same value for $k$ is used with the same private key $D_A$ to sign two different messages, then anyone possessing the two messages $m_0$ and $...
0
votes
1answer
316 views

Is there a library-less implementation of DSA available to read? [closed]

Is there a pedagogical library-less implementation of DSA available to read? (Not ECDSA.) Obviously BigInteger and hash functions may be from libraries, but I want to read the implementation of all ...
1
vote
1answer
264 views

With ECDSA is there a way for the verifier to calculate any properties of $k$?

With ECDSA, given $(r,s)$ and $m$, is there a way for a verifier to calculate any (boolean) properties of $k$, without knowing $k$ or the private key $D_A$? (I understand that $k$ should be random, ...