0
votes
0answers
6 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 ...
-1
votes
0answers
26 views

Evidence of practical differential cryptanalysis attacks

Are any ciphers routinely cracked using techniques derived from differential cryptanalysis or is brute-force historically the only practical attack against ciphers? I ask this because DES was ...
0
votes
0answers
18 views

How the couples of int (n,e) and (n,d) are converted into char for RSA public and private keys?

Let us consider the private key (5,7) how is this converted into a RSA public key file such as : ...
0
votes
0answers
11 views

Adding a Random component to CBC MAC in order to enlarge the tag space

CBC MAC that is using AES as the underlying block cipher, has tag space of 2^128. If we add a random single block, concatenating it with the tag, and encrypt it again in AES CBC mode, with additional ...
0
votes
0answers
10 views

Known plaintext attack to CFB mode

How does a known plaintext attack on a block cipher in CFB mode work? I only see the following: If an attacker knows the plaintext $P_i$ he can recover the key $K_i = C_i \mathbin{\oplus} P_i$ from a ...
0
votes
0answers
9 views

Paillier cryptosystem preserve ordering of sums for two integer sequences

According to Paillier cryptosystem the product of two ciphertexts will decrypt to the sum of their corresponding plaintexts. I have two separate integer sequences X and Y that have same number of ...
0
votes
0answers
19 views

Software applications to learn cryptography

I am a student of cryptography. I want to start learning about software needed in this field, for example Cryptool. Could you help me and introduce some applications to me?
0
votes
0answers
9 views

Permuted vectors

Consider we have two vectors $v_1, v_2$ of size $n$, and each vector contains $n$ elements. We permute the vectors as: $\pi (k_1,v_1), \pi (k_2,v_2)$. Where $\pi (k_i,v)$ denotes a permutation of a ...
4
votes
1answer
41 views

Can cycle finding techniques reduce the memory usage of the MitM attack against 2DES and 3DES?

A 2DES like cipher $c=E^{(2)}_{K_2}(E^{(1)}_{K_1}(p))$ where both halves have an $n$ bit key is vulnerable to a meet-in-the-middle attack. Meet-in-the-middle using a big table Create a table ...
-1
votes
0answers
25 views

Creating of finite field over small prime number for Elliptic Curve

I need automatically generate field over small prime number for Elliptic Curve over Fp. For example I have Fp=23 and a=1, b=0. So filed has 23 points. Each point has to satisfy this equation: ...
2
votes
4answers
65 views

Password length versus hash length?

If a system hashes passwords with a 256-bit long hash, are passwords (which are not necessarily alphanumeric, can be any value per byte (0-255)) longer than 32 bytes useless under the context in which ...
4
votes
1answer
64 views

Adding two public keys

secp256k1 (the signature scheme used by Bitcoin) has the interesting property that you can add two public keys to get a combined key that requires both private keys to produce signatures for. Is ...
1
vote
1answer
26 views

Where is the authentication tag stored in file encrypted using AES-GCM?

So I am using cryptopp to encrypt a file in a project and I am using AES-GCM. I have a 256bit key and a 128bit ivec and a 128bit tag that I use to encrypt files. However, I want to know where the ...
1
vote
1answer
11 views

Key iteration count while using random keyfile larger than master key

If I were to have a 4096-bit file of random data (/dev/random) used as a keyfile for LUKS, would there be any benefit to having a key iteration count higher than 1? My reasoning is that the attacker ...
7
votes
2answers
985 views

If you hashed a hash an infinite number of times would you end up with a unique hash?

If you took a hashing algorithm for example MD5 and repeatedly passed the output hash back into the algorithm an arbitrarily large number of times would you eventually end up with one unique hash? My ...
1
vote
1answer
19 views

Use of Lamport's Signature as a primitive

Is Lamport's One Time Signature used as a primitive to construct any other cryptographic protocols?
0
votes
0answers
30 views

El Gamal Decryption with Big Numbers [on hold]

I have a message decrypted in ElGamal. I was wanting help on how to decrypt it. Here is the data that I was given. a p value, a g value, a h value, a x value, a y value, and a c value How would I ...
2
votes
1answer
132 views

How does ROTL work?

what does ROTL stand for? I know it does left shifting but what about the acronym? When we do a left shift, do we take the leftmost bit and add it at the end, by making the second bit the first, and ...
1
vote
1answer
38 views

Image sharing without data overhead

The idea is to share n images among n persons so that all images can be reconstructed by someone in possession of all shares. However, there must not be any data overhead (which means the shares sent ...
0
votes
1answer
22 views

SHACAL-2 vs. AES as underlying block cipher for Secure Hash (aka SHA-256)

The hashing scheme SHA-256 (for instance) is based on Merkle-Damgard construction with the underlying compression function based on the block cipher SHACAL-2 configured in Davies Meyer mode. SHACAL-2 ...
-3
votes
0answers
26 views

can you solve exercise 1.20 Stinson [on hold]

Can you help me for solve exercise 1.20 of "Stinson" text book? Excuse me.I have no time to write the exercise.
0
votes
1answer
16 views

Figure 2 in the Verifiable Computation - Pinocchio

I am reading the Pinocchio paper (verifiable computation): http://research.microsoft.com/pubs/180286/pinocchio.pdf The paper is rather hard for me. For the Figure 2, I guess $v_1(x)$ should be ...
0
votes
0answers
19 views

Decoding Base64 encoded password with internal hashing [on hold]

I was given a username and encoded password list to decode. The list came from an export function of Cyberoam firewall (physical device), and was a .csv Username,Password,Email list. I expected the ...
1
vote
1answer
50 views

Can a cryptographic hash be used as a cryptographic RNG?

Say I roll a six sided die 200 times (6^200 = ~2^517) and string all the results together into a long string of numbers and hash then result with SHA-512. Can I use that result for cryptographic ...
3
votes
1answer
55 views

Non adjacent form of an integer is unique

I have tried to look up the proof for NAF (Non-adjacent form) being unique for every integer, but as far as I have seen, textbooks only mention it as a property of NAF, but no proof is given. Also I ...
2
votes
1answer
20 views

Is this transposition cipher information-theoretically secure for 1 message?

Given: $m = \{0,1\}^{n}$; a plaintext message of length $n$ encoded in binary $k = randomshuffle([0, 1, ..., 2n-1])$; A secret key consisting out of unique numbers between 0 and $2n-1$ in a true ...
1
vote
1answer
47 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 ...
1
vote
0answers
41 views

How to securely map an element from an smaller domain to the other element in a large domain

Problem: I have a small sized domain, say s-bit. It's clear that the probability for an adversary to guess an element is $ \frac{1}{2^s}$. I need to make the probability negligible. However, I need to ...
0
votes
1answer
28 views

RSA: Why must e be relative prime to phi(n) [duplicate]

I've got a question concerning fields used in RSA: Let's use the following symbols for my example: {p,q} = primes {e,n} = public key {d,n] = private key I learnt that an inverse element exists if a ...
0
votes
0answers
44 views

Montgomery Reduction

I'm taking a hardware cryptography class and working on a problem that focuses on Montgomery Reduction. So by definition: Computing a x b (mod N) Pick R, s.t. R > N, gcd (R,N) = 1 Compute N^-1 ...
0
votes
1answer
46 views

Which one these alternatives using authentication and encryption will solve this multiple-user database problem?

Which one these alternatives using authentication and encryption will solve this multiple-user database problem ? I'm trying to understand the field of cryptography, so I've started reading a ...
3
votes
0answers
60 views

Prime factorization

What is the largest integer that can be factored by modern algorithm like Msieve and GGNFS in a time less than 5 hours with normal computers? For example, can an integer like ...
0
votes
0answers
39 views

Encryption of plain text using stream cipher algorithm

We know that in stream cipher algorithms plain text and generated key are Xored byte by byte. Generated key depends on how much plain text there is and on that basis key will generate and plain text ...
-2
votes
0answers
19 views

Can anyone provide a simple java code for bilinear pairing? [on hold]

Can anyone provide a simple java code for bilinear pairing? (using API/without using API) How does pairing work with JPBC? Thanks.
0
votes
1answer
25 views

What is the signifcance of inside threat in “How to Construct Multicast Cryptosystems … Secure Against CCA2”

In How to Construct Multicast Cryptosystems Provably Secure Against Adaptive Chosen Ciphertext Attack, the paper states under preliminaries: We consider the scenario where a single party, called ...
0
votes
0answers
32 views

How to Exchange Random Coin Flips between Two Untrusted Parties [duplicate]

I'm not sure if this belongs here, but my friend and I were wondering if there was a good algorithm to exchange random coin flips to make some random decision between two untrusted parties without the ...
0
votes
0answers
42 views

Is there are code hidden in Wired Magazine's December 2014 Issue?

There seem to be several hints that there's more to Wired Magazine, December 2014 (Issue 22.12) that meets the eye. In his Letter from the Editor, Scott Dadich says: I’ll refrain from spoiling ...
4
votes
2answers
42 views

Has human-generated entropy ever been a real problem?

I know the topic of human brains generating random numbers has been discussed here and in Cognitive Sciences before, but I am interested in a particular part of it: In an introductory book to ...
0
votes
1answer
22 views

Swap $x$ and $k$ in GGM construction

I'm studying the Goldreich-Goldwasser-Micali construction from pseudo-random generators to pseudo-random functions. In this specific construction, assume $G:\{0,1\}^n\rightarrow \{0,1\}^{2n}$ is a ...
0
votes
1answer
58 views

Common Modulus Attack in RSA

Consider the following scenario: The Information Security Department (ISD) of an organization issues each of the organization's employees, domestic and abroad, with an individual RSA key. To simplify ...
0
votes
0answers
23 views

Generating interactive, secure multiple ECC key pairs deterministically

In Elliptic Curve Cryptography (ECC) assuming user A has a private public key pair of $S$, $P$ accordingly with generator point $G$ which as we know is: $$P=S*G$$ Assuming that user A wants to ...
0
votes
0answers
19 views

Is it possible to transform an x-coordinate of ephemeral elliptic curve point?

I would like to know: Is it possible to transform an x-coordinate of ephemeral elliptic curve point using a pre-shared secret key (e.g. password) and also it should be without any known attacks like ...
0
votes
1answer
53 views

what is number of invertible matrix m*m on$ z_n$? [on hold]

‎ ‎‎please help me what is number of invertible matrix $‎m*m$‎‎‎ on Group $\mathbb{z}_n$ ?‎‎‎, assuming we know‎ this number in $\mathbb{Z}_p \quad$ (‎p is prime‎‎) is $‎(p^{n}-1)(p^{n}-p) ...
3
votes
2answers
401 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
21 views

Deterministic outputs based on non-connected inputs

I am looking for a one way function that can generate outputs deterministically. However, revealing any of the inputs dont allow the person to generate other inputs. E.g: lets say we have a list of ...
1
vote
1answer
50 views

How are onetimepads distributed?

OTP encryption is unbreakable as it seems. I have read some stuff (wiki, blogpost, etc.) but i would not find any information how they are used. If i wanted to create a messenger service, how would i ...
0
votes
0answers
35 views

Determine encryption method with input and output

A website stores username and password in a session cookie. In the cookie the password is "encrypted" or modified in some way. Given that the "encrypted" version is always the same, I do not believe ...
1
vote
1answer
31 views

How to generate the APA SBox?

I am trying to generate the S-Box provided in the Affine Power Affine paper (PDF) but I'm not sure I understand it fully. The essence of the paper is this: ...
4
votes
0answers
66 views

Is the reverse of the “discrete logarithm problem” equally dificult? [duplicate]

It is not easy to understand why this becomes a hard problem. The discrete logarithm problem as defined here: “any integer k that solves $b^k = \{g\mod{n}\}$ is termed a discrete logarithm” i.e.: ...
1
vote
1answer
46 views

NTRU and one failed example

In NTRU crypto system I have used these polynomials and parameters: $N = 17, p = 7, q = 64$ and $f$ as private key is: $$f = -1 + x + x^2 - x^4 + x^6 + x^9 - x^{10}$$ So the inverse of $f$ in ring ...

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