All Questions

3,163 questions with no upvoted or accepted answers
Filter by
Sorted by
Tagged with
4
votes
0answers
380 views

XTS and 256-bit data blocks

I am developer of an application that uses XTS with ciphers which use 128-bit blocks (AES, Serpent and Twofish). I now want to use XTS with a cipher which uses 256-bit blocks (Shacal-2). AFAIK, I ...
4
votes
0answers
67 views

Election communication protocol

I'm not a cryptography expert, but this seems like it falls into this area. Imagine I want to design an election system (senate race for example) where I send the exact same ballot of 100 candidates ...
4
votes
0answers
103 views

Creating an SPN cipher from ChaCha20 or Salsa20's double round function

Given that ChaCha20's building blocks have been also used to construct a hash function, can the double round function from either ChaCha20 or Salsa20 be used to construct a secure SP-network cipher? ...
4
votes
0answers
118 views

Committing to a secret shared value

Suppose I run a multiparty protocol. At the output stage, I have the function output in a secret shared manner among all parties. Now I want all the parties to commit to their value of the secret ...
4
votes
0answers
156 views

Does length prepending fix the key reuse problems with CBC and CBC-MAC?

As I hope everybody is well-aware, re-using the key for CBC-MAC and CBC is a really bad idea. Now, there's also the paradigm to prepend the message length to the CBC-MAC (as "associated data") to ...
4
votes
0answers
220 views

How secure is $\operatorname{AES256}_{\operatorname{ECB}}(\operatorname{ChaCha20}(\text{plaintext}))$?

Suppose I encrypt a bytestream using ChaCha20, and then encrypt the resulting ciphertext using AES in ECB mode. How secure is the combination?
4
votes
0answers
519 views

Password hashing in embedded systems

Are there good options for password hashing in embedded systems? These systems often cannot afford slow hash functions. I can think of a few approaches: Store the (hashed) passwords in a HSM that ...
4
votes
0answers
607 views

Can a secure MAC break if the adversary is given oracle access to Verify?

In the Mac-forge experiment, the adversary is given access to a tag-generation oracle, which generates a tag for each message given by the adversary. The adversary's task is to generate a valid tag on ...
4
votes
0answers
1k views

What is the difference between mutual authentication and unilateral authentication both ways?

I am currently reading Engineering Security by Peter Gutmann, on page 7 he states: proper mutual authentication is quite different from unilateral authentication in both directions He references ...
4
votes
0answers
127 views

An MPC protocol from Elgamal is a good solution a homomorphic multiplication?

I want to compute a multiplication between many secret values and then distribute the result to everyone involved. For this, I thought about an MPC protocol built from Threshold Homomorphic Elgamal. ...
4
votes
0answers
237 views

How can I implement decryption for NTRU homomorphic encryption scheme?

I have come across this paper On-the-fly multiparty computation via on-the-cloud Multikey from Fully Homomorphic Encryption by Lopez-Alt et al., where authors describe a NTRU-based homomorphic ...
4
votes
0answers
121 views

Why reveal MAC-keys after using them?

As far as my understanding goes MACs are used to determine whether the received message comes from a source that has access to a MAC-key which is known by both parties. Some crypto protocols reveal ...
4
votes
0answers
110 views

How about a homomorphic integer sorting in a MPC context?

I want to implement the ATV-FHE scheme as described by Adriana López-Alt, Eran Tromer, Vinod Vaikuntanathan: On-the-Fly Multiparty Computation on the Cloud via Multikey Fully Homomorphic Encryption (...
4
votes
0answers
100 views

What followed findings of A. Lenstra et al. concerning shared factors of practical RSA moduli?

A. Lenstra et al. had a paper in 2012 "Ron was wrong, Whit is right", in which one reads: "What surprised us most is that many thousands of 1024-bit RSA moduli, including thousands that are contained ...
4
votes
0answers
486 views

Elliptic Curve Blind Signature Implementation

I have seen this prior post: Elliptic Curve based blind signature implementation Currently I'm sizing up how difficult it would be to attain Elliptic Curve Blind signatures for an application I'm ...
4
votes
0answers
87 views

Are there any real-world E-voting systems in use with the Paillier cryptosystem?

There are a lot of theories of Paillier cryptosystem with references to e-voting. Are there any real-world E-voting systems in use with the Paillier cryptosystem?
4
votes
0answers
304 views

How did G.H. Hardy's work contribute to today's public-key cryptography?

I know that Hardy's work in number theory was used by Clifford Cocks in 1973 to develop the basis for public-key cryptography. What specifically was this work, and how is it used today in ...
4
votes
0answers
452 views

Can convergent encryption be turned into deterministic authenticated encryption with HMAC?

If you take a convergent encryption algorithm and replace the hash $H$ used to derive the key with HMAC-H, keyed with a secret key $k'$, does the resulting algorithm provide you with deterministic ...
4
votes
0answers
237 views

Explanation of part of a visual cryptography algorithm

I have been working on a project involving visual cryptography and I am stuck with the following problem. My question is related to this paper, AN IMPROVED VISUAL CRYPTOGRAPHY SCHEME FOR SECRET ...
4
votes
0answers
243 views

IES: What security has the asymmetric primitive to provide?

I think most of us know the notion Shoup introduced of KEM/DEM (Key Encapsulation Mechanism / Data Encapsulation Mechanism) which is used for example by the (famous) ECIES, where the key is the hash ...
4
votes
0answers
135 views

Anonymisation resilient to key leak

Problem statement Elbonian citizens have been issued a card holding a random $B_j\in\{0,1\}^b$, $0\le j<2^n$, $b\ge n+20$ (representative example $b=64$, $n=28$). The habit has grown to use this ...
4
votes
0answers
159 views

Using machine-learning techniques for data-dependent operations in ciphers

From 'Methods of Symmetric Cryptanalysis' by Dmitry Khovratovich, The data-dependent operations are one of the most controversial design concepts. We say that an operation is data-dependent, if it ...
4
votes
0answers
213 views

As a cryptographer, what are the things I should care about in my implementation of pairing functions?

As a beginner in cryptography, I do not know anything about different pairing types more than their names. So far, I know these names: Ate pairing, tate pairing, eta pairing, and r-ate pairing. I am ...
4
votes
0answers
173 views

ECIES: Purpose of optional shared information?

According to Wikipedia the ECIES algorithm has two optional shared information $S_1$ and $S_2$. They are used as follows: Generate a random shared secret $Z$ according to ECIES, which will never be ...
4
votes
0answers
133 views

Implementation Attacks on Hashes

So I am familiar with attacking implementations of block ciphers via side channel attacks, cache-timing attacks, etc. What implementation attacks are there against hashes or hashed based functions (...
4
votes
0answers
205 views

understanding the proof of knowledge

Recently I've been reading the paper “A New Family of Implicitly Authenticated Diffie-Hellman Protocols”. It's very hard for me to go further. Especially when it comes to the proof of knowledge. ...
4
votes
0answers
201 views

Feasible way to check n-dimensional equidistribution of PRNGs

I am currently gathering some test methods and test suites for random number generator qualities, and am a bit stuck at finding something feasible to test for n-dimensional equidistribution. As input ...
4
votes
0answers
289 views

Secure Secret sharing

I'm trying to come up with a new way to do oblivious transfer that is faster and requires less computation than existing methods. The basis of my method is shamir secret sharing. Below is an example ...
4
votes
1answer
213 views

FHE over the integers - Is that paper's scheme known to be insecure against quantum adversaries?

I was reading the paper Fully Homomorphic Encryption over the Integers, and started wondering if there is a known quantum attack on their main scheme, because There is an efficient quantum attack on ...
4
votes
0answers
498 views

Using the same private key for two ECC key pairs

Let $(d_1,Q_1)$ and $(d_2,Q_2)$ be ECC key pairs over two different elliptic curves (say NIST P-224 and NIST P-256). According to the Elliptic Curve Discrete Logarithm Problem (ECDLP), if the private ...
4
votes
0answers
258 views

Obfuscating point-like functions

There are standard schemes for obfuscating a point function; I'm wondering if we know how to obfuscate a slight generalization of a point function. I'll elaborate more precisely. Definition 1. A ...
4
votes
0answers
713 views

Key expiration policy for 3DES / TDES / Triple DES

I have a system that signs plain text messages using a message authentication code (MAC) encrypted with 3-key Triple DES. The short message is used on connection to establish a session key, so it ...
4
votes
0answers
165 views

Is MITM possible after key exchange phase done successfully in RSA?

Is MITM attack theoretically possible after public/private key pair exchange is done successfully. Say Alice and Bob have genuine public keys of each other. Is MITM possible further during ...
4
votes
0answers
423 views

Storing password or derived key in keychain?

Currently I am developing an application that stores and reads encrypted data. The data is encrypted with AES and the actual AES key is derived from the users password (and some nonce) with PBKDF2 ...
4
votes
0answers
123 views

A confusion about linear span of modified de Bruijn sequence

Recently i'm reading "Cryptographically Strong de Bruijn Sequences with Large Periods" . In the section 2 2.1 Basic Definitions and Properties , property 1 says ...
4
votes
0answers
384 views

How hard is a known prefix hash preimage attack on SHA-2?

Suppose the attacker knows $X, Z$ such that $H(X || Y) = Z$ If bit-length(Y) < 60 then a brute force attack is possible. What if ...
4
votes
0answers
444 views

How can Alice and Bob safeguard their message exchanges against replay attacks?

Assume Alice and Bob communicate over an insecure channel using one-time perfectly-secret encryption together with one-time secure message authentication code. Say Eve has the ability to eavesdrop and ...
4
votes
1answer
186 views

Lattice-based cryptography prone to side channel attack?

Is lattice-based cryptography still prone to side channel attacks? What are some mitigation strategies, if any?
4
votes
1answer
110 views

VIC cipher author known?

Does anybody know if the design of VIC cipher is attributed to anybody? I've tried Google and found nothing. There are quite a few sites describing the method in detail, a few implementing it ...
4
votes
1answer
193 views

Generating random vector for Full Homomorphic Cryptography

The site below explains that part of doing homomorphic encryption, you need to generate a vector of random numbers that have the property that its dot product against a randomly generated bit vector ...
4
votes
1answer
2k views

Effective key length of Two-Key Triple-DES

What's the effective key length of Two-Key Triple-DES, for some (possibly several) reasonably well-defined and sensible definitions of effective key length, say assuming attack using ample chosen ...
3
votes
0answers
55 views

Does varying ChaCha rounds add any security?

This paper introduces 'Freestyle' a randomized, and variable round version of the ChaCha cipher. It uses the concept of hash based halting condition, where a decryption attempt with an incorrect key ...
3
votes
0answers
59 views

Constant time arithmetic implementation in DSA

I am trying to understand why it is a hard problem to have formally verified constant time arithmetic for DSA when compared with ECDSA. For instance, in ECDSA implementations of OpenSSL, we have ...
3
votes
0answers
46 views

Boneh DDH Paper - Sampling Integers in Random Reduction

I've been reading Dan Boneh's DDH paper, in particular section 3.1 which covers DDH randomized reduction. The first two sentences of theorem 3.1 state: Let $\Bbb G = \{G_p\}$ be a family of finite ...
3
votes
0answers
46 views

RSA accumulator exclusion proof without set

In researching about RSA accumulators I came across this question, Inclusion and Exclusion proofs in RSA accumulators - from the first answer I had assumed that proof of non-membership could be ...
3
votes
0answers
109 views

Criteria for public modulus of RSA accumulator

What are criteria for generation of an RSA public modulus used in an RSA accumulator, and their rationale? Are there special requirements in some sub-cases, like for «one-way» accumulators? Josh ...
3
votes
0answers
71 views

Is AES-GCM-SIV with fixed IV deterministic authenticated encryption?

Is there any functional or strong security difference beyond speed between AES-GCM-SIV with implicit fixed public IV and no additional data AES-CTR (or AES-OFB) with 128-bit IV computed per HMAC-SHA-...
3
votes
0answers
108 views

Is there any real attack deployed on the CTR mode over history?

The CTR mode, with its CPA security, is one of the malleable block cipher mode of operations. An attacker can simply modify the bits of the ciphertext stream in their advance. This is due to the lack ...
3
votes
0answers
51 views

trust-less blind execution environment (thought experiment)

I apologize for the theoretical nature of this question, but It has cost me a lot of sleep over the past months. Querying my immediate peers has so far failed to produce results. I assume this ...
3
votes
0answers
45 views

Inconsistency Between NIST SP800-108 and KBKDFVS

I am attempting to implement a Key Based Key Derivation Function (KBKDF) in Counter Mode as part of a larger project. To test my implementation, I was directed towards the Verification System for this ...

15 30 50 per page
1
3 4
5
6 7
64