# All Questions

2k views

### Signal vs Telegram in terms of protocols?

Some time ago, the question was asked in chat, why MTProto (Telegram's protocol) is supposedly worse than Axolotl (Signal's protocol) as both protocols have been the inventions of their respective ...
686 views

### Hardness of finding mutual discrete logarithms of small generators in $\mathbb{Z}_p$

Suppose you want to select a prime $p$ such that finding e.g. $\log_2(3)$ in $\mathbb{Z}_p$ is expected to be either at least as hard as the general Discrete Logarithm Problem in $\mathbb{Z}_p$, or at ...
207 views

### AMD and RDRAND instruction

The latest AMD programmer manuals, dated June 2015, include the RDRAND instruction in the instruction set. For completeness, it lacks ...
686 views

### Who first published the interest of more than two prime factors in RSA?

Multi-prime RSA is now a well known technique (described here): it uses $k>2$ distinct secret prime factors in the public RSA modulus, with the advantage that, using the CRT, we can gain a speed ...
105 views

### Turing's (still?) classified inference engine algorithm?

Does anyone know the algorithm used by Turing's Colossus inference engine, so highly classified that the Brits kept it secret for decades after WW II? Indeed, it may still be classified. Several ...
293 views

### How were shift amount constants in MD5 found?

The md5 specification gives a series of 4 rounds to execute over a 16-word block. Each round has a repeating sequence of 4 shift amounts (s in ...
457 views

### Security of RSA for paranoids with padding?

RSA for Paranoids (RSAP) (in cryptobytes v3n1), also known as Unbalanced RSA, is a variant of RSA proposed in 1995 by Adi Shamir, as a mean to increase the RSA public modulus size while keeping ...
77 views

### K friedman - two texts explanation

I have a question, I read the k friedman test to determine the period of a vigenere cipher text, and I understand something like this: Friedman's K test tries to find out what period of the cipher by ...
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### What is the fastest modular reduction algorithm available?

I have been browsing for the fastest and most efficient modular reduction algorithms and came across quite a few. But the one in A Fast Modular Reduction Method (2014) by Zhengjun Cao, Ruizhong Wei ...
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### help with cryptanalysis of a sponge permutation

I have been studying and researching hash functions. So far my research has led me to the sponge construction. It appears that the permutation used in the sponge to stir the state is more or less ...
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### 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. ...
30 views

### OTR AKE protocol implementations security

While looking at the different versions of OTR protocol I discovered a strange thing: there is no trace of the patch for the weaknesses that were noted in “Finite-State Security Analysis of OTR ...
31 views

### Understanding the definition of HGD

On the section 4.2, page 10, of the paper Order-Preserving Symmetric Encryption, the authors define two subroutines: the first one is called $HGD$ and the second one is $GetCoins$. I have doubts ...
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### Performance of ECDSA, ECKCDSA and ECGDSA

It is proven that ECDSA algorithms are faster in key and signature generation compared to RSA. In addition, the signatures are much shorter. However, I would like to know the performance difference ...
74 views

### Why is AES-SIV not used, but AESKW, AKW1?

I'm trying to investigate different key wrapping algorithms for my implementation. I've noticed that AES-SIV is very rarely implemented by most of open source libraries. Most of them implements key ...
77 views

### Rule 30 Cellular Automaton for Cryptography

Steven Wolfram of Mathematica uses a pseudorandom number generator based on Rule 30 for applications in Mathematica software but I would like to know if a pseudorandom generator based on Rule 30 is ...
98 views

### Proof that perfect privacy implies that the number of keys is at least the number of messages

I was reading a proof to the statement: Perfect privacy implies that $|K| = |M|$ where I am pretty sure that $K$ is the set of keys and $M$ is the set of messages. The proof is the following, ...
118 views

### Efficient way to confirm identity

I am working on a multiplayer game. I have a central server which handles all data transmission and coordinates all games. Clients which involved in a single session send requests to do actions to ...
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### Is it possible and safe to use SAKKE for signing/verification, rather than for encryption?

Is it safe to use the Sakai–Kasahara key encryption algorithm (SAKKE) for signing/verification, rather than for encryption? (Example at bitbucket.org) In particular, I want many Bobs to be able to ...
46 views

### Can a one-way accumulator be used in place of a digital signature?

Could a one-way accumulator be used in a manner to replace a digital signature? Can it provide a way to: verify that the data has not been tampered with, and verify that the message is in fact ...
278 views

### How to break a columnar transposition cipher?

I'm currently studying for a cryptography exam. I've been given ciphertext that has been encrypted by a columnar transposition cipher. I've been given no shift key length or key word, the only thing I ...
65 views

### Elliptic curve point addition with $Z_1 = Z_2 = 1$

Elliptic curve point addition and point doubling operations using Projective and Jacobian coordinates require fewer field multiplication operations when considering $Z$ coordinates of input points ...
32 views

### Safe generation of $k$ points on a curve such that the mutual discrete logs are hard?

I have a multiplicative group $G$ of prime order $p$ implemented using a twisted Edwards curve (similar to Ed25519). I want to compute a set of $k$ distinct points $P_1,...,P_k$ that generate $G$, ...
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### Would the encryption of bigrams and trigrams weaken the code?

Supposing a rotor machine of the 1940s or 50s, with 36 characters instead of 26. Would the encryption of the ten additional characters as the most frequent bigrams or trigrams weaken the code? What ...
266 views

### What is the original SKID3 protocol?

While searching for a mutual authentication protocol I often stumbled upon SKID3. However I encountered different variations of it. The basic structure is the following: (1) A --> B: rA (2) B --> ...
331 views

### Evaluating Algebraic Complexity of a S-box

While studying the design and the desirable properties of an AES S-box , I came to know that Algebraic Complexity is also an important property of an S-box which is usually considered while evaluating ...
117 views

### Homogenous and heterogeneous Unbalanced Feistel Networks

Unbalanced Feistel networks can be homogenous (F-function identical in each round), or they can be heterogeneous (F-function not always identical in each round). The advantage of heterogeneous UFNs ...
256 views

### Given a 'good' basis for a lattice, how can we solve the CVP?

I'm doing a little bit of reading about lattices. I read that if we can find a 'short' basis for our given lattice, we can solve CVP and SVP very efficiently. However, the paper didn't describe an ...
302 views

### LT codes with Homomorphic hashing

I have been working on a project implementing LT codes with Homomorphic hashing (inspired from http://blog.notdot.net/2012/08/Damn-Cool-Algorithms-Homomorphic-Hashing and ...
329 views

### Odds of false error detection in a randomness test using the chi-squared test?

Common Criteria classifies the requirements for true Random Number Generators, and specifies how these should be tested against failures (these can occur accidentally, or following deliberate attack, ...
72 views

### Is correlation in vector distributions “dangerous”?

Consider the two vector distributions $\xi,\chi$ described below, each one outputting integer vectors of length $n$ with coefficients in $\{0,\dots,n\}$. Distribution $\xi$ samples each coefficient ...

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