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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BER or DER X9.62 for ECDSA signature

The signature format for ECDSA signatures can be encoded using ASN.1 integers according to X9.62 or it can comprise of two integers with the same size as the key size. In case the X9.62 format is ...
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Elliptic curves for ECDSA

I'm trying to implement parameters generation for ECDSA according to SEC1 v2.0: ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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Curve25519 over Ed25519 for key exchange? Why?

I've been reading up on the Signal Protocol (in this PDF) and it seems to be using Curve25519 for ECDH and EdDSA (with Ed25519) for signatures. My question is why not use only Ed25519? This ...
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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 ...
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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 ...
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Should different key pairs be used for signing and encryption?

In the recent iOS Security white paper from Apple (February 2014), the section on iMessage discusses using two different asymmetric key types as part of its standard operation: When a user turns on ...
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Why can we not use the group $Z_{p}^{*}$ for cryptography?

Sorry if this is a noob question, but for instance in ECDSA, we start by considering the field $\mathbb F_p$, whose the elements also form a group under multiplication. Why don't we just use this ...
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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'...
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X9.62 Multiplying an elliptic curve point by a number

I'm currently trying to implement ecdsa and the first problem i met -- multiply an elliptic curve point by a number. As far as i understand X9.62 gives some recommendation for doing it but i haven'...
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Is there any weak message for an ECDSA signature?

Suppose ECDSA is used without hashing the message, but directly using a short message (say 10-bytes long) as the value z (using the definitions at http://en....
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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 ...
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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. ...
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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 ...
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How can I use Weierstrass curve operations with a=-3 for implementing operations for a=0?

I am working with golang's elliptic library. It implements functions on Weierstrass elliptic curves with $a=-3$. I need to make my own library that allows me to handle curves with $a=0$. I understand ...
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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 ...
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Is it usual for a signed message to contain the public key of the signer?

In protocols/systems which use ECDSA, is it common for the message to contain the public key of the message signer? If not, how do recipients know that the message has been signed by the correct ...
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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,...
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Can Alice send Bob a secure message with only DSA and no key exchange?

Suppose Bob has a DSA key pair, and Alice has Bob's public key. Is there any secure way that Alice can send Bob a message only he can read if Bob can not send any reply? I think the answer is no, ...
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Isn't the deterministic property of (EC)DSA a security problem?

From what I read in Wikipedia's article "Elliptic Curve DSA ~ Security", the "deterministic" generation of $k$ can help prevent certain type of attacks (such as the one happened to Sony). However, ...
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Why doesn't this replay attack work on ECDSA?

I've just started working with elliptic curves and ECSDA in particular, so my understanding of the underlying math isn't great. The thing I'm currently stuck on is trying to understand why replay ...
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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 ...
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EdDSA (Ed25519) is any random number sufficient for a good private key?

Looking at a reference implementation it shows that the key pair generation simply does: read X bytes from RNG and then derive another value from these X bytes thus producing private key with derived ...
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Is DSA vulnerable if verifier doesn't check r' > 0?

If a DSA implementation neglects to check $r' > 0$ when verifying signatures, what are the consequences? Creating a forged $s$ would seem to require solving for $k$ $g^k mod\ p = nq$ which is ...
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How to generate a public key from a private ECDSA key?

Having some specific ECDSA curve and a private key, how does one calculate the public key? I am having a hard time finding the algorithm and equations for it.
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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 $k$. ...
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Why are digital signatures used when performing DH?

Suppose the server has a public key which everyone knows is associated with it, maybe it's hardcoded into the browser or signed by some CA. At no point do you need the server to sign anything with it,...
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Public-key format for ECDSA as in FIPS 186-4?

What is the public-key format for ECDSA as in FIPS 186-4, and where is it formally defined? In particular, are there variants beyond Cartesian coordinates? Is that a pair of bitstrings, or a ...
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Why do we truncate the hash when using DSA?

All the articles I read on the web about DSA keep telling me that the size of the hash needs to be truncated so that the bit length is equal to or lesser than the bit length of the prime number of the ...
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Adding two public keys

secp256k1 (the signature scheme used by Bitcoin) has the interesting property that you can add two public keys to get a combined key that requires both private keys to produce signatures for. Is ...
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Exactly what RNG weaknesses endanger (EC)DSA?

RFC 6979 defines deterministic variants of (EC)DSA. It states in introduction One characteristic of DSA and ECDSA is that they need to produce, for each signature generation, a fresh random ...
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Storage of Private Keys

I'm building a bitcoin web application that will require all users to be assigned a wallet for adding funds to their account. I plan on exposing the public key to the user (the bitcoin address). Users ...
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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 ...
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Academic papers on ECDSA security

What are the most authoritative papers on the security analysis of ECDSAs? I`m mainly looking for comparisons of how secure different curves are considered to be, what potential methods are there of ...
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Are there public $p$ and $q$ numbers for use in DSA?

There are many RFC documents giving large primes to use in Diffie-Hellman. However, I couldn't find standards on the $p$ and $q$ large primes used in the DSA signature scheme. This is proving to be a ...
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Why not to use curve over field of $p^m$ with $p > 2$ for ECDSA?

I'm reading the ECDSA paper and they say you can only use ECDSA with odd-power fields $p$ or with binary fields $2^m$. Why not other power prime fields?
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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 ...
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Which hash is used when providing signature algorithm ED25519 or ED448?

From TLS 1.3 there are two signature algorithms using edDSA: /* EdDSA algorithms */ ed25519(0x0807), ed448(0x0808), All the other signature-...
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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 ...
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Recovering private key from Secp256k1 signatures

I've seen many answers here and many articles that says we can recover the private key from reused R signatures. But, what if the r,s signatures are different in transaction of bitcoin then is there a ...
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Does the size of a ECDSA key determine the hash algorithm?

I am a bit lost in understanding what I read on authentication, signature, etc. For instance, is the size of the ECDSA keys produced by ssh-keygen -t ecdsa -b 256 ...
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Safety of DSA key parameters sharing

I'm looking for a solution to use in a context where I need to be able to generate new asymmetric key pairs quickly (using a widely recognized algorithm, and EC-DSA is not applicable). It sounds like ...
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Atomic multi-party commitments

Alice and Bob publicly choose the messages $M_A$ and $M_B$ and independently sign them (Alice privately signs $M_A$, Bob signs $M_B$). Now Alice and Bob are looking for a protocol that allows them to:...
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Is it secure to ECDSA-sign a public key without hashing it first?

I am trying to sign an ECDH public key with ECDSA. However, my hardware does not allow me to implement a hash algorithm, considering I am running out of memory already. Therefore, I am currently just ...
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Signing a GCM MAC

If I encrypt a message with AES-GCM, is it safe to use the MAC as the hash in a DSA/RSA signature? That is, if someone knows the AES key and nonce, will they be able to generate a different message ...
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Are (EC) DSA blind signatures possible?

I've been searching for a way to create blind ECDSA signatures. My research and experimentation has led me to believe that this is not possible. I've been attempting to articulate why and I think ...

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