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Questions tagged [signature]

Algorithms and protocols for creating signatures to documents, and verifying such signatures. These are normally asymmetric, for symmetric signatures see [mac].

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Temporal or spatial digital signatures

Digital signatures allow authentication of content based on a secret held by the signing entity. Are there any existing schemes, proposals or even services for letting "location" or "time" sign the ...
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Which organization is responsible for certifying a TSA?

I see there a number of free TSA services according to this page (not all are still in service). In other sources I see references to the requirement of audits for the TSA to be 'rfc3161 compliant'. ...
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Why is timestamp response still valid after scrambling bits?

Using BouncyCastle for crypto, I am successfully able to create and validate RFC3161 timestamps. Everything seems to work fine with normal data and usage. I am doing some manual error evaluation and ...
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What is the smallest size of CAdES signature?

CAdES signatures are usually huge, they contain certificates, possible full chain, and even source data enveloped in it. This is very impractical if we want to sign every file in the system for ...
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1answer
37 views

Efficient Aggregate Signatures With Same Key

Suppose Alice has a set of messages $\mathcal M$ and generates signature pairs for each message $(m_1,s_1)$, $(m_2,s_2)$, ... $(m_n,s_n)$ using the same key. She then transfers these signature pairs ...
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Could you design something like a ring signature that uses website accounts instead of keys?

Ring signatures allow one to prove that you own a private key corresponding to a public key from a set of keys, without revealing which private key you control. This is useful if you are part of some ...
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2answers
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Is there any way to check signed documents in a group of people without knowing who signed which?

Let's say there are 3 people A, B, C. Everybody knows their public keys. They sign documents/messages and normally we can know who signed which by checking with their public keys. Is there any way to ...
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1answer
54 views

How does Diffie Hellman protocol work in Bitcoin Blockchain Transactions?

Greetings to all! Please explain how the Diffie-Hellman protocol works in Bitcoin? That is, in Blockchain Transactions, there is also a total number of "K" recipient and sender? "K" the recipient and ...
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1answer
85 views

Generating RSA signature, by manipulating shorter message signatures?

Given a server that can return me RSA sign for any plaintext shorter or equal length of the given plaintext (excluding the given plaintext), how can I fraud/get the sign of the given? $$sign = M^{d} \...
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Fail to Sign/Verify signinature in C# [migrated]

I am trying to use the .Net RSA functions to sign a Hash, but when i try to Sign the hash and then verify the Signed string it turns out false... Is this the wrong place to ask? (Is this more of a ...
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maskGenAlgorithm for RSA signature with PKCS1-PSS padding [migrated]

I am generating RSA signature using RSA_PKCS1_PSS_PADDING. I am setting digest algorithm as SHA256 using EVP_get_digestbyname() and EVP_DigestSignInit(). And salt length parameter as -1 using ...
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1answer
53 views

Message authentication vs entity authentication

Does message authentication authenticate the entity? If the answer is "No", because message authentications like MAC work with the shared symmetric key, then my second question is: Does a message ...
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1answer
67 views

Comparable or partially homomorphic public key derivation for signatures?

Are there any public key signature schemes that can be compared blindly or partially homomorphically based on the private key without knowing the private key? Example: let's say I derive a public key ...
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2answers
87 views

Why Random Secret Necessary Almost in all digital Signature Algorithms

I've read some introduction documents about digital signatures, and all they said is Signer calculates a hash of data to be signed. This hash is encrypted with the private key. Verifier reads the ...
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1answer
55 views

Digital signature

I learned that a digital signature is encrypted using private key and is decrypted using public key. How does the verifier gets the public for verifying the signature? If a person has to request ...
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1answer
65 views

Security of Fast Two-Party ECDSA Signing

The paper "Fast Secure Two-Party ECDSA Signing" by Yehuda Lindell describes a system in which two parties, $P_1$ (with 1/2 of a share of a long-term ECDSA signing key $x_1$) and $P_2$ (with the other ...
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1answer
63 views

How to break RSA signature on XOR of hashed blocks

I'm trying to figure out if there's a way of breaking or weakening the following method of signing long messages Given $M=m_{1}m_{2}...m_{n},\,\,|m_i|=64b, \,\,h=h(m_{1})\oplus h(m_{2})\oplus\cdots\...
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Is it necessary to transmit two or three points of an elliptic curve?

Are there cryptographic protocols, where a party should transmit by communication channel simultaneously two or three $\mathbb{F}_q$-points of an elliptic curve over a finite field $\mathbb{F}_q$? ...
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Trying to verify a download signature with PGP, but getting “no signed data” when passing in the .asc file? [migrated]

I tried the following steps from Verifying Signatures on the Tor Project: gpg.exe --keyserver pool.sks-keyservers.net --recv-keys 0x4E2C6E8793298290 imported: 1 ...
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1answer
32 views

Help understanding lattice-based aggregate signature scheme

I came across this paper about aggregate lattice-based signatures, however, I'm not able to fully understand it. Specifically, I'm wondering if someone could help answer the following questions: In ...
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2answers
68 views

Does this pairing-based signature scheme work?

Suppose $g$ is a pairing-friendly elliptic curve with subgroup generators $G_1$ and $G_2$. Suppose also that $M$ is the message I want to sign. Setup Compute $A = a \cdot G_1$ and $P = p \cdot G_2$, ...
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Intuition for CL signatures security

I'm trying to understand why the CL signature scheme (PDF) works only under the strong RSA assumption. Other well known signature schemes like ECDSA, Schnorr and even RSA can be proven secure only in ...
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1answer
61 views

Does this simple signature scheme work?

Let's say my public key is defined as $P = p \cdot G$, where $p$ is my private key and $G$ is a generator point of an elliptic curve. If I wanted to sign a message $m$, could I do the following? Hash ...
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1answer
44 views

Can a TLS certificate using ECC secp384r1 as PK algorithm uses RSA for signature

If a TLS certificate public-key algorithm is ECC secp384r1 or ECC prime256v1, is it possible to have RSA as a signature ...
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1answer
82 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 ...
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1answer
58 views

Does RSASSAPSS use RSA signature

I just need to know is it correct to classify the RSASSAPSS scheme and sha[256 | 512 | 1]WithRSAEncryption all under RSA ...
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2answers
81 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 + ...
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1answer
101 views

Mathematics behind the paper “how to leak a secret” for ring signature

I'm reading the paper "How to Leak a Secret" (Rivest, Shamir, Tauman; 2001). On page 8/14, in chapter 3.4, the authors present the following "combining function": $$C_{k,v}(y_1, y_2,\ldots,y_r) = ...
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1answer
48 views

The goal, the method, and the interface of the signcrypt primitive.

Some time ago, I proposed making the site more educational by teaching correct cryptographic programming. The proposal had had somewhat good reception, but was met with cold ice as there had been ...
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1answer
37 views

ECDSA Signing and verifying signatures between Python and JS [closed]

I create a signature on js, here jsrsasign Signatures are obtained in the format: ...
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1answer
60 views

Fiat-Shamir paradigm and the forking lemma

I am reading the proof by Pointcheval and Stern and by Bellare and Neven about the forking lemma. The papers discuss the security proof of digital signatures by applying the lemma. It seems also ...
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1answer
237 views

RSA PSS security advantage

To my humble opinion, please correct me if I'm wrong, RSA-PSS (PKCS#1 ver 2.1) advantage over RSA as described in PKCS#1 ver. 1.5 is in its security proofs. Does this proof and the advantage is still ...
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1answer
52 views

Unable to reproduce correct signature data

"Skatteetaten" is the Norwegian tax authority. We're currently trying to implement signing of messages for digital cash registry systems and i'm not able to reproduce the desired signed data. Went ...
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1answer
79 views

Does the One-Time Hash-based Signature Scheme render Ring Signatures useless?

On the Bitcoin community, to maintain privacy, they recommend using one-time spend addresses. CryptoNote, Monero et al. prefer Ring Signatures to maintain that privacy. There are some issues regarding ...
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1answer
40 views

ED25519 Child Key Derivation

Let's say I generate a keypair for a user with go's ed25519 package: pub, private := ed25519.GenerateKey(nil) And I want to generate additional child keys as ...
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1answer
58 views

Hash and sign via trapdoors for lattices

Both the papers GPV'08 and MP'11 present trapdoors for lattices that allow to recover $s\in\mathbb{Z}_q^n$ and the error vector $e\in\mathbb{Z}_q^m$ when given $y=As+e$, for $A\in\mathbb{Z}_q^{m\times ...
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1answer
46 views

Is the only use for the private key of a root certificate signing certificates issued by it?

A root certificate can be used to issue intermediate certificates. The private key of the root certificate is needed in order to sign any intermediate certificates. However, after that, we only need ...
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1answer
49 views

What are the different use cases between an HMAC and digital signature? [duplicate]

I understand that both an HMAC and digital signature are used to check the integrity and authenticity of a message. Further, I understand that a digital signature is non-repudiatible. What I do not ...
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1answer
46 views

Need help understanding public key format of Barreto-Naehrig signature

I have a 256bit signature and a certificate with a public key to verify it. I had little information about the signature scheme used, but I know now that it's "ECBNwithSHA256". I have never come ...
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1answer
61 views

Challenge - Response protocol - how to incorporate client randomness

I am designing a challenge-response protocol to enable a client to authenticate to a server. The client has a private key, and a certificate (issued by a trusted CA). At this point in the protocol, ...
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2answers
278 views

Curve 25519 (X25519, Ed25519) Convert coordinates between Montgomery curve and twisted Edwards curve

I have some misunderstanding about EdDSA conversion coordinates between Montgomery curve and twisted Edwards curve. In https://tools.ietf.org/html/rfc7748 I see that a base point for Curve25519 is ...
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1answer
59 views

Is a digital signature of use if you don't also encrypt the message containing it?

I'm sure this has been asked before. Its just too blindingly obvious. from wikipedia "Digital signatures, in which a message is signed with the sender's private key and can be verified by anyone who ...
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2answers
116 views

What's wrong with this digital signature scheme?

With regards to user authentication... The server sends Alice a randomly chosen number. Alice signs the number and sends the signature back to the server. The server checks the signature using Alice'...
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2answers
106 views

Cryptography scheme to prove you really are the author for something

Say I'm a researcher like Satoshi Nakamoto that wants to stay anonymous. I want to publish documents and sign them somehow. A few years, I want to reveal my identity and prove it was me who was ...
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1answer
58 views

Could we use a more efficient hash for signature generation?

Is it possible to use a more efficient hash - such as one based on GHASH - instead of a cryptographic hash for signature generation? In other words, could a combination of a fast hash and the private ...
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2answers
165 views

Digital signature providing a proof of file authenticity

How can a digital signature provide proof the authenticity (not integrity!) of a file?
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2answers
61 views

Does the Server Key Exchange sign a hash or text

In TLS 1.2 when using ECDHE_RSA, the ServerKeyExchange message contains a signature over the server's ECDHE public parameters. My question is: Is the signature over ...
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1answer
47 views

Commitment in two party protocols

I have been reading Fast Secure Two-Party ECDSA Signing by Lindell, and I see that in key generating and signing (pages 9-10, especially visible from Figure 1), only the first party performs a ...
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1answer
96 views

Need help with NFC Tags and cryptography

I have some NFC-Tags, which will be added to my devices. These NFC Tags are basically EEPROMs with an unique UUID (7-Byte, readonly, public) and some constant parameters (approx. 7-15 Bytes, read and ...
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1answer
67 views

Why would my certificate's signature algorithm differ from its keys' signature algorithms?

I have a signing certificate that I'm loading into an X509Certificate2 object in Visual Studio. I can't get my head around why the certificate itself has one ...