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

learn more… | top users | synonyms

1
vote
3answers
121 views

How is the following different than RSA Signing of a document?

If the goal is to demonstrate that you are who you say you are, I think the following will work: Bob wants to know that you are Amy. Bob encrypts a number using Amy's public key and then asks her what ...
2
votes
1answer
266 views

Hash collision resistance requirements for Lamport signatures

According to the original paper, Lamport one-time signature scheme uses two one-way functions: $F$ and $G$. The former one, $F$, is used to create a public key by hashing elements of the private key ...
0
votes
1answer
126 views
+50

Proof for composed signatures

Assumes that we have 3 signature algorithms, $S^A$ with key pair $(sk^A,pk^A)$, $S^B$ with key pair $(sk^B,pk^B)$,$S^C$ with key pair $(sk^C,pk^C)$. We denote by $\epsilon$, $\epsilon'$ and ...
8
votes
1answer
135 views

Proof of Communication

I desire an algorithm in which Alice sends a block of data $X$ to Bob, with proof that the data was both sent and received. Ideally this would take the form of a public-key signature of the block $X$ ...
1
vote
2answers
98 views

Efficiently map $2^n$ unique 64-bit vectors to $2^n$ $n$-bit vectors where $n < 64$? [closed]

Is there an efficient way to map $2^n$ unique 64-bit vectors to $2^n$ $n$-bit vectors where $n < 64$?
6
votes
1answer
561 views

Why are MACs in general deterministic, whereas digital signature constructions are randomized?

The fact is I'm not quite sure if my question statement is true, however all the MAC constructions I know of (e.g. CBC-MAC, CMAC, HMAC) are deterministic, whereas many constructions for digital ...
1
vote
1answer
575 views

Is Curve25519-java secure?

I have only about 2 weeks of cryptography experience mostly in the form of questions on bitcoin.se. Is Curve25519-java up to date with current Curve25519 standards? Is Curve25519 itself secure? ...
3
votes
2answers
195 views

Rely on NSA Suite B Cryptography?

NSA's Suite B Cryptography suggests some cryptographic algorithms for encryption, digital signatures, message digests and key agreements. The selected algorithms and their key size are suggested by ...
-2
votes
1answer
32 views

How does the signature checking work in DKIM?

As far as I understand DKIM works like this: DKIM is not used to encrypt anything, the only purpose is to mark mails that are not really sent from the claimed domain as spam. the DKIM-enabled ...
1
vote
1answer
60 views

Verification of signed message with encryption

I have a question about the message that is being encrypted and signed. Say, two users called Tom and Mary, both have a pair of private key and public key. Tom sends a message through a system that ...
1
vote
1answer
135 views

A way around digital signatures?

Scenario: I have to protect the integrity of some files that will be exchanged between entities $A$, $B$, $C$. Entity $A$ creates the file (e.g. configuration) and sends it to $B$ and $C$. Entities ...
4
votes
1answer
190 views

What characters are valid in PGP encrypted and signed messages?

What characters may be present in a PGP encrypted message or a PGP signature? For example, do encrypted messages only use the Roman alphabet + some numbers and symbols? Can the character set be ...
3
votes
1answer
227 views

Relation between attack and attack model for signatures

I would like to know: What is the relationship between an attack and an attack model. For example, let $\Pi$ be the Lamport signature scheme. This signature has it's security based on the one-way ...
4
votes
0answers
275 views

Reasons for Chinese SM2 Digital Signature Algorithm

In the IETF RFC draft named "SM2 Digital Signature Algorithm" a signature algorithm is specified. The RFC does however not mention why this signature algorithm has been defined. Nor does it specify ...
3
votes
2answers
132 views

What are good combinations of public key algorithms or primitives for long term security?

There has been talk in literature about doing multiple encryption with different block ciphers or stream ciphers several times before, and the benefits and risks of such efforts. There may be hidden ...
4
votes
1answer
120 views

Implementing CD serial key system

I am trying to create a system where to unlock the application one needs to enter a serial code. I have read many articles on the theme but there are two problems bugging me. One is, If I have a ...
1
vote
2answers
235 views

Digital Signature using symmetric key cryptography

Generally digital signature is a public key cryptography concept.But it needs high overhead. So is there any publication or link available where 'digital signature using symmetric key' has been ...
3
votes
2answers
131 views

Merkle Tree High Tree

I'm reading Merkle tree signatures and I like know if the security of the that scheme depends, also, of the high of the tree or only depends that hash function is resistant to collision?
6
votes
4answers
179 views

Authenticating data generated by a particular build of an open source program

[I was torn between posting here or security.stackexchange.com. In the end, I felt that this was more of a design question, rather than an implementation question and so chose this forum.] My ...
2
votes
2answers
155 views

What curve and key length to use in ECDSA with BouncyCastle

I'm developing a client/server system in Java which is not interacting with third party software, so I don't have to worry about compatibility. At a certain point, I need the client and server to ...
2
votes
1answer
261 views

RSA 896 vs 1024 vs 2048 in Javascript?

I am currently working on a secure messaging website and I had been using RSA 2048 for encryption, decryption and signing of messages but I found it to be EXTREMELY LAGGY so i've moved to 1024. I did ...
3
votes
1answer
139 views

Description of signatures with message recovery (as in ISO/IEC 9796-2 and EMV Signatures)

I'd like to get an overview of how the signatures with message recovery work, especially in case EMV and other smart card systems. Is there a nice overview available without being required to read the ...
6
votes
2answers
108 views

Is there a way to compress multiple signatures of the same data?

So, I'm working with a system that allows individual users to each have their own private-public key pair. I would like to allow multiple users to use their private key to sign the same piece of ...
3
votes
1answer
107 views

What is the quantum-resistant signature scheme with the smallest signature + pubkey?

After playing cat and mouse with an number of quantum-resistant signature schemes and coming up with nothing with small enough signatures, I'm turning to Crypto.SE. I need a quantum-resistant ...
7
votes
2answers
183 views

Linkable ring signature scheme

I need an implementation of linkable ring signature, a ring signature which allows identifying whether two signatures belong to the same signer. It has important privacy-related applications, like ...
1
vote
0answers
63 views

Is there a malleable pubkey digital signature scheme?

I'm trying to find a special kind of Digital Signature Scheme. The scheme should allow me to transform a signature $s=\text{sign}(sk,m)$ (for a private key $sk$ and a message $m$) into a signature ...
2
votes
0answers
65 views

Is it possible to perform a rudimentary asymmetric key encryption algorithm by hand?

I have at least three, distinct motivations for having a simple way to use asymmetric key encryption by hand or without modern computers. First, I was recently demonstrating to a 12-year-old how ...
3
votes
0answers
76 views

Compact digital signature for noisy data

The question asks for a signature scheme, with a public verification procedure, that is tolerant to minor alterations of the signed data during its transmission [possibly in analog form over some ...
3
votes
2answers
103 views

Is ”generating transcripts that are indistinguishable from actual messages in a signature scheme” not universal forgery?

In the Pointcheval paper “Security arguments for digital signatures and blind signatures”, they have proved the security of Schnorr signature for existential forgery under adaptively chosen-message ...
4
votes
4answers
211 views

What is the difference between authenticating and signing a document?

Authenticating a document means to verify it is from the sender. But it seems like signing a document also verifies it’s from the sender. What exactly is the relationship or difference between ...
1
vote
1answer
65 views

How can a digital signature algorithm incorporate a random data if it is to be authenticated on a separate system

I am trying to understand how RSA digital signatures can incorporate any data from a PRNG into the final signature. Does this mean that separate implementations might fail to verify each others ...
2
votes
1answer
339 views

How is digital signature different from a message authentication code (MAC)?

I know the definitions of both but can't specifically tell how they are different and if one is better than the other. Please help.
0
votes
1answer
119 views

Digital signatures under plain RSA

Show that digital signatures under plain RSA are insecure (Plain RSA means that signing is done by calculating $m^d\bmod n$, with $0\le m<n$, and no padding or hashing of $m$). Write an algorithm ...
1
vote
1answer
87 views

how to use salt to sign a message and how is it effective? [duplicate]

I've had an assignment to sign a file using hash and salt, so I read about salt and I got why it's important when it comes to password, but not to sign messages. How do I sign something using salt? ...
2
votes
0answers
80 views

Looking for a detailed example of proof by reduction

I'm looking for a very detailed example of proof by reduction. Say we have two or three protocols (that have been proven secure) and we construct a new protocol. We want to provide a proof of security ...
2
votes
1answer
328 views

Precomputation attacks on RSA

Are precomputation attacks - such as outlined in RFC 3610 chapter 5 - possible on RSA PKCS#1 v1.5 signature generation? If yes, are such attacks taken into account when calculating the cryptographic ...
3
votes
1answer
222 views

Why does Openssh use only SHA1 for signing and verifying of digital signatures?

I am learning SSH protocol. With my current understanding of SSH protocol, I think that message digest algorithms for using in digital signature should be derived from Key Exchange. But Openssh ...
1
vote
0answers
213 views

Most frequently used digital signature schemes in the recent years

I am looking to understand if there are any hard figures on which digital signature schemes are most commonly in use today. I'm only really interested in what is employed recently (ie. last couple ...
3
votes
3answers
163 views

Does ECIES imply authenticity?

Assume: Alice and Bob both generate separate EC keypairs Alice obtains Bob's public key, and together with her private key creates a shared secret key Alice encrypts a message using the shared key ...
1
vote
1answer
71 views

Is there an anonymous non-interactive authorisation scheme with peer-side auth. signature generation?

I implemented a pseudonymous PKI scheme (by K. Zeng @Springer Link), where all peers can change their public keys including its signature on their own. I am looking for a way to extend it with some ...
6
votes
2answers
1k views

Why hash the message before signing it? Digital signature with RSA

Here's a method to sign the message with RSA: Why hash the data before signing it? Why not sign the whole message? It'll save time if you sign the hash value, but I've heard there are also security ...
1
vote
1answer
90 views

Ed25519 with R replaced by H(RAM)?

Ed25519 signatures consist of $(R, s)$, where $s = r + H(RAM)a$ $mod$ $l$, and $R = rB$. This differs from the Schnorr signature where instead of $R$, the signature contains the hash $h=H(RAM)$. ...
1
vote
1answer
67 views

ElGamal digital signature. why mod p-1 in delta?

Im trying to figure out why $\delta$ in the signature part of ElGamal has mod $p-1$ when $\gamma$ has mod $p$? $\gamma = \alpha^k \mod p$ $\delta = (x-a\gamma)k^{-1} \mod p-1$
0
votes
1answer
117 views

Is this EdDSA modification secure?

I am hoping to employ a signed set membership system which is valid iff each signer's contribution to the set is present. The system should allow for two or more mutually exclusive signed sets to be ...
1
vote
1answer
139 views

Why should a signature use PSS padding in RSA?

Suppose I send a message using AES (private keys already negotiated securely) and I send a hash of this message using RSA (encrypted with private key) with OAEP to verify the authenticity and ...
1
vote
0answers
58 views

The advantages of Merkle Signature and One time Signature

In Merkle Signature, it also requires one-time signature to be used once for a message. The signature in Merkle scheme is even longer compared to Lamport one time signature. The verifier also has more ...
1
vote
1answer
112 views

Group Signature Scheme without Opening but with Revocation

After reading many papers about group signature schemes, I saw that basically all of them employ the possibility of "signature opening": The Group Manager (GM) can identify any signature made by his ...
3
votes
1answer
124 views

Security benefits of Ed25519 generating signatures deterministically

I am reading on the Ed25519 curve, and I am trying to understand a claim. Here is the claim: Foolproof session keys. Signatures are generated deterministically; key generation consumes new ...
4
votes
1answer
166 views

Proving the possession of signature in zero-knowledge

Does anybody know an efficient mechanism to prove the possession of a digital signature (e.g. RSA) on a certain attribute (message) in zero-knowledge? That is, without revealing the actual signature ...
1
vote
2answers
107 views

Is RSA encryption the same as signature generation?

Is performing RSA encryption with the private key identical to performing RSA signature generation (signing)?