3
votes
1answer
63 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 ...
1
vote
1answer
19 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 ...
0
votes
0answers
8 views

GMAC implementation in C

Anyone please provide some reference on open source implementation of GMAC in C or C++. It'd be good if someone can refer AES_GCM implementation that can be used for GMAC authentication only.
1
vote
0answers
8 views

Is this variant of SRP useful?

I'm interested in using a modified form of SRP as a peer-to-peer authentication method. Since neither side is acting as a host, one of the primary design goals for SRP (that the client doesn't need ...
2
votes
1answer
25 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
35 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 ...
3
votes
2answers
269 views

Does SRP reduce to DH key exchange when shared password is not secret?

I can find JavaScript implementations of SRP (Secure Remote Password protocol), but nothing that inspires confidence for Diffie-Hellmen key exchange. I also have a separate need for SRP later. I ...
2
votes
4answers
167 views

Computation indistinguishability questions

The definition I have is: Two probability ensembles $X = \{X_n\}_{n \in \mathbf{N}}$ and $X = \{Y_n\}_{n \in \mathbf{N}}$ are computationally indistinguishable if for every probabilistic ...
-1
votes
0answers
34 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 ...
5
votes
1answer
43 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 ...
0
votes
0answers
20 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 : ...
8
votes
2answers
1k 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
48 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 ...
0
votes
0answers
14 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 ...
2
votes
4answers
66 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 ...
0
votes
0answers
24 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
11 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
10 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
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 ...
-1
votes
0answers
28 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: ...
1
vote
1answer
32 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
39 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 ...
2
votes
1answer
136 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 ...
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
12 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 ...
2
votes
1answer
67 views

Comparing n-multiple amount of merkle trees?

I would like to know what best steps are there in finding differences between a high order amount of merkle tree's or if a better associative structure should be used. I ask this questions because ...
0
votes
1answer
23 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 ...
2
votes
2answers
289 views

SHACAL in SHA-256

I was reading about hash functions, namely SHA, and I read that it is made of the Merkle-Damgard construction. And then the text said that the compression function used is based on the Davis-Meyer ...
0
votes
0answers
51 views

S-Boxes and SP-Network

I work on an exercise and I have to study functions as : $ f : \mathbb{F}_q \rightarrow \mathbb{F}_q$ with $q = 2^n$ which can define a S-Box for SP-Networks. There is a question that I can't answer ...
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 ...
-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 ...
-3
votes
0answers
308 views

RSA encrypted in logarithm. Is it right or wrong? [closed]

Factorization and primality test of Lepore-Santo in 4*log [(Y-X)/6]+1 I will show you the basic example, that i sto say the factorization of two prime numbers because reterating this process we can ...
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 ...
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 ...
19
votes
4answers
14k views

Can you help me understand what a cryptographic “salt” is?

I'm a beginner to cryptography and looking to understand in very simple terms what a cryptographic "salt" is, when I might need to use it, and why I should or should not use it. Can anyone offer me a ...
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 ...
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 ...
4
votes
2answers
43 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
0answers
45 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
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
0answers
62 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
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
2answers
1k views

Why does second pre-image resistance imply pre-image resistance

I am studying hash functions. I can understand why collision resistance implies second preimage resistance, but I don't get why second preimage resistance should imply first preimage resistance. ...
1
vote
2answers
225 views

Multiple private keys for single public key

I am currently working in security in mobile ad-hoc networks. I have several clusters, and I want to send some data encrypted with its public key, from the cluster head to the cluster members. I ...
0
votes
0answers
42 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.
3
votes
2answers
402 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
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
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 ...

15 30 50 per page