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

3
votes
1answer
25 views

More efficient and just as secure to sign message hash using Ed25519?

According to the Ed25519 paper, the (potentially long) input message is hashed twice (see http://ed25519.cr.yp.to/ed25519-20110926.pdf Section 4 page 12 steps 1 and 3). The webpage ...
1
vote
1answer
36 views

Signature Verification: High level

I'm trying to understand how certificate signing and verification works conceptually. I know the classic example with asymmetric cryptography- the sender encrypts data with public key of receiver, ...
4
votes
2answers
145 views

Signature and hash function properties

I understand the need for the hash function to be collision resistant and second pre-image resistant. For what reason, exactly, does a hash function need to be pre-image resistant? If this property ...
-3
votes
2answers
81 views

What needs to be proved for a cryptosystem to be secure?

For example showing that it is easy to produce ciphertext from plaintext but is difficult/impossible to get plain text from ciphertext. I am asking in general but am more interested in asymmetric ...
4
votes
1answer
88 views

Deterministic ECDSA signatures?

ECDSA signatures depend on parameter k that is chosen by the signer. As a result, there are many signatures for the same private key d and message m. What I want to achieve is a deterministic ...
0
votes
1answer
80 views

How many bits to flip in an RSA public key to do signature forgery?

Scenario: Alice wants to verify a signature from Bob. Alice knows Bob's RSA public key (e, n). However, Alice is getting the data, the signature of the data and the public key from an attacker Eve. ...
1
vote
0answers
35 views

One-Time-Signature based codes

I'm trying to understand the sentence in bold, in the follow paragraph of A new one-time signature scheme from syndrome decoding Keygen: Given a security parameter $\lambda$, choose a suitable ...
0
votes
0answers
7 views

What if the Local Windows Cert Store is Compromised? [migrated]

The diagram below illustrates chaining digital certificates up to a publicly trusted Root Certificate: I have been researching how trusted root authorities (such as GlobalSign or Verisign) are used ...
2
votes
1answer
38 views

N users must approve a request

I have a locked-down production system that we'd like to process specific requests, picked-up (poll) from a less-secure location. For security and "go slow, this is production" reasons, a request ...
0
votes
1answer
20 views

Stern identification scheme to signature scheme

I'm trying to understand the comment in the page 103 of the book Postquantum Cryptography. about convert the identification Stern procedure for signing. Can you write an example of signature of this ...
1
vote
0answers
45 views

How far is public-key crypto involved in “banking world”? [closed]

I would like to know how public key cryptography is used in the banking world. I am not looking for big details, but for example: Are banking card embedding a private key used for signing ...
0
votes
0answers
20 views

RSA: If I sign the same digest with same key twice, will the signatures be identical? [duplicate]

If I don't have public keys to verify the signature, can I use this to discover that two signing services are using the same key? Can you send a reference?
3
votes
2answers
74 views

Does authenticated encryption add any protection to a signed digital envelope?

The general scenario of hybrid encryption is to use public key cryptography for the exchange of a one time session key that can be used for the encryption of the plaintext with a symmetric encryption ...
1
vote
0answers
25 views

RSA Signature Forgery

We all know that x509 certificates carry a signature that represents the certificate digest encrypted by the private key of the issuer. I believe that the digest is encrypted only providing one ...
3
votes
1answer
98 views

what are the advatanges and disavantages of the digital signature algorithms for JWT?

I am using a Java JWT library jose4j. There is a list of digital signatures algorithms which can be used. HMAC using SHA-2 RSASSA-PKCS1-V1_5 Digital Signatures with with SHA-2 Elliptic Curve Digital ...
3
votes
1answer
113 views

Proof that two parties can communicate

Suppose we have three parties, Alice, Bob, and Carol. Alice can receive messages from Bob and Carol individually, but can only send messages to both simultaneously. Additionally, Alice cannot tell if ...
1
vote
0answers
32 views

Digital signature in a group chat scenario?

I understand that RSA is great for 1-to-1 digital signature. In the group chat of N people, other than storing and maintaining N public keys, is there a simpler way of authenticating each and everyone ...
1
vote
1answer
85 views

Is there a scheme that allows to use RSA based challenge response protocol limited to signing only 8 bytes to create a secure signature of any data?

I have a tiny device that has a challenge-response authentication mechanism where the device signs 8 bytes of any data with it's internal 2048 bit RSA key. I would like to be able to certify any data ...
1
vote
1answer
124 views

Why isn't Rabin-Williams cryptosystem widely used?

I think we all know RSA. And of course we also know DJB (a.k.a. Daniel J. Bernstein). Now some already have noticed that he has an opinion towards cryptographic questions. In his 2008 paper ("RSA ...
1
vote
1answer
28 views

Why does P1363 require RW signature with $0 ≤ s < n/2$?

I'm using an older copy of P1363 Public Key Cryptography was used below. It may (or may not) reflect the current state of affairs. P1363 has the following requirement in section 8.2.8 IFSP-RW, p. 45: ...
2
votes
0answers
23 views

Residue requirements of Rabin-Williams primes?

I'm trying to determine the residue requirements of Rabin-Williams. An older copy of P1363's Public Key Cryptography states the following in Section 8.1.3.2 RW key pairs: An RW public key consists ...
1
vote
1answer
44 views

Tweaked Square Roots and Rabin-Williams

I'm reading Bernstein's RSA signatures and Rabin–Williams signatures: the state of the art. In section 6, Bernstein states: Recall that Rabin’s system needed to try several values of r, on ...
1
vote
1answer
39 views

Winternitz Signature Scheme Verfication

I am reading page 39 in this "Post Quantum Cryptography" book. Why does equation 15 hold? There is no further knowledge about f and you definitely cannot use any power laws. So, why is ...
1
vote
0answers
52 views

Why is public key cryptography not widely used in governments? [closed]

Are there any practical limitations? Govt driving license, passport, SSN could be digitally signed making it easy for anyone to validate. They can have a qr code in them which can be easily validated ...
0
votes
0answers
65 views

Name of this attack?

I am studying Merkle tree signature. Let $\sigma=(s,Y_s,\sigma_{\text{OTS}},As)$ be a signature of certain document. Here $s$ is the index of leaf, $Y_s$ is the respectively OTS public key and $A_s$ ...
1
vote
1answer
55 views

The difference in size between ECDSA output and hash size

So if I use secp256k1 for example, I've got my key size of 256 bit, and say I sign a SHA256 hash of a message, with size 256 bit, I get an output of size 512bit. Why is there a difference between the ...
0
votes
1answer
58 views

RSA Signature : Process of Sign the message and Verify

I have read that the RSA numeric signature works as the following: Generation of keys : $p,q,N,e,d$ Process of signing the message $m$ (which is BigInteger) : it uses the secret key $sk=(p,q,d)$ so ...
0
votes
0answers
22 views

Is sending encrypted message and signed message a secure way of transmitting data? [duplicate]

I know that the industrial standard is normally sending data in the following format: Send Encr(msg, Sign(msg)) Is the following way a secure as well? ...
1
vote
1answer
51 views

Are digital signatures using preprocessed paper pads possible?

My idea was, given that a computer could produce some sort of lookup tables on paper, could then a human use those lookup tables to create a system for digital signatures? This was really an idea for ...
0
votes
0answers
32 views

Does “identity-based dynamic threshold signature” exist and could such scheme contain a “Signature Combination” algorithm?

I came across [1] and I'm very puzzled by this paper. They use a building block which they call "identity-based dynamic threshold (IBDT) signature", citing paper [2]. First of all [2] does use this ...
1
vote
1answer
55 views

Can Winternitz be easily converted to a many-time encryption scheme?

The Winternitz scheme is typically cited as being an OTS scheme. Can it also be used as a one-time encryption scheme? If it can be used as a one-time encryption scheme, then is it possible to easily ...
1
vote
1answer
57 views

Rabin-Williams, blinding and size of Integer r?

I was reading the paper Breaking the Rabin-Williams digital signature system implementation in the Crypto++ library. The library uses blinding, but it was not enough to stop key recovery. But my ...
2
votes
1answer
86 views

Asymmetric cipher with multiple public keys

Asymmetric cryptography is well known. You generate a private key. Using the private key you generate a public key. Then you can sign a message with the private key and check signatures using the ...
5
votes
2answers
508 views

Why use randomness in digital signature algorithms?

I understand why randomness has to be employed in encryption, because deterministic ciphers are not IND-CPA. I don't understand why digital signature schemes that employ randomness, like RSA-PSS, are ...
0
votes
1answer
134 views

SSL / TLS digital signature exchange

If server is sending its digital signature, in which message / where does the digitally signature is provided to the client. Is it after the server_hello message because there the public key of the ...
1
vote
0answers
78 views

BER or DER X9.62 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 ...
2
votes
1answer
124 views

What use is the signature without the message under RSA?

Using RSA for signing & verification, is there a way to take a valid signature for an unknown message, and for someone else to generate a valid signature using a different key against the valid ...
0
votes
1answer
67 views

anonymous signature implementation and usage?

This is one of the question asked in my class. Implement a anonymous digital signature. So it means hiding signers information. i could not find any article in anonymous digital signing. Also another ...
0
votes
1answer
123 views

PKCS#7 signed data structure in signed PDF document

Is it mandatory to include PKCS#7 data (OID 1.2.840.113549.1.7.1) octet string into the sequence of PKCS#7 signed data? I mean if you want to sign PDF, you are basically adding PKCS#7 container ...
2
votes
1answer
75 views

Device intercommunication with commands

I want to create a smart house project, and in that I bought some simple RF modules. Those modules don't support crypto out of the box but I want to connect them to a device that I would program to ...
1
vote
1answer
129 views

Collision attacks on digital signatures

After reading this document about MD5 collision attacks, I still don't understand how collisions can make digital signatures insecure. In the paper, the researchers created two files with the same ...
5
votes
0answers
93 views

How can ECDSA signatures be shortened (to be used as a product key)?

So I made my own serial key generation software, using ECDSA, for use in my own applications and it works great so far! To keep the serial key short enough I use a 128 bit EC curve. My final signature ...
4
votes
1answer
60 views

Do asymmetric signatures require constant-time verification?

To avoid a timing attack, HMAC signatures are usually compared in constant-time (every byte is compared, and the results aggregated). Is the same necessary for asymmetric signature algorithms such ...
0
votes
1answer
97 views

Why not send the identity in the encrypted message?

I've recently started reading the book "Applied Cryptography" written by Bruce Schneier. Quite a few times I stumbled across protocols who send the identity outside of the encrypted message (see step ...
2
votes
1answer
99 views

Given only RSA public key parameters, what security issues might I be able to detect?

I'm attempting to automate some checks against a large list of .NET assemblies, and want to include a test to see if the RSA parameters used to sign the assemblies are sensible. However, since I don't ...
0
votes
0answers
40 views

Signature constructor using Self-signed certificate

I've the following scenario: One application signs JWT access/id tokens using the private key contained in a self-signed certificate, and then passes its public key to other parties to validate that ...
1
vote
1answer
63 views

RSA padding confusion attacks

Server A produces signed messages on request. You can tell server A what type of RSA padding to use in the signature (either RSASSA-PKCS1v1_5 or RSASSA-PSS). Either way, the message will be signed ...
1
vote
0answers
63 views

Can CKM_RSA_PKCS signature be made secure by lowering its maximum input size?

The CKM_RSA_PKCS Mechanism in PKCS#11 v2.20 section 12.1.6 PKCS #1 v1.5 RSA is a signature scheme commonly used to implement RSASSA-PKCS1-v1_5 of PKCS#1 signature of data hashed externally to a ...
0
votes
1answer
24 views

Reordering of multiple signed blocks

I would like to refer you to page 430 of the Handbook of Applied Crypto, where the authors said "... reordering of multiple signed blocks presents a security risk..." This statement was made in ...
1
vote
1answer
123 views

How do SignRecover and VerifyRecover work?

In PKCS#11, there are the SignRecover and VerifyRecover methods, where the data can be recovered from the signature. How do these methods work? Can I implement signrecover and verifyrecover with ...