0
votes
0answers
5 views

Matsui's Linear attack on DES P box

I'm trying to understand Matsui's linear attack on DES and I have something I don't understand in his paper. In his paper he say that: $NS_{5}(16,15)=12$ (which is OK) and from that he say that: ...
0
votes
1answer
5 views

Looking for encryption algorithm not subject to known-plaintext attack with IV reuse

I've encountered an interesting problem where we can basically say the following: We need to encrypt messages, but we have no room to store IVs. We can synthesize IVs; however an attacker would be ...
-1
votes
0answers
11 views

Prove that one-way functions cannot have polynomial-size ranges

Namely, prove that if f is (even weakly) one-way, then for every polynomial p(·) and all sufficiently large n’s, it holds that |{f (x) : x ∈ {0, 1}^n}| > p(n).
0
votes
1answer
20 views

How to attack the Two Time Pad?

I encrypt 2 random keys with the same 'one' time pad. You can get both encrypted keys. You don't know anything besides the size. Is there a way to attack the two time pad in this scenario? And what ...
1
vote
1answer
13 views

How do revocation certificates work in PGP?

I've already read how to build and upload them, but I'm wondering how revocation certificates work, what informations they hold and so on. Suppose my private key is compromised, but I have a ...
0
votes
0answers
14 views

arithmetic calculation problem to quadratic arithmetic program

I am reading the Pinocchio paper (verifiable computation): http://research.microsoft.com/pubs/180286/pinocchio.pdf The paper is rather hard for me. I am considering this calculation problem: ...
-1
votes
0answers
22 views

Is it possible to use edwards curves with ecdsa?

I have only seen edwards curve with ecdh, hence the question.
0
votes
1answer
29 views

How to generate an elliptic curve and compute its order

I'm trying to wrap my head around invalid-curve attacks on ECC, and I'm reading this example and trying to implement it using Sage. I am following well until this part: B generates elliptic ...
0
votes
3answers
31 views

Question about decryption

I have a question about decryption. Let's say I have a bunch of files that are encrypted. Someone gains access to those files, and finds out that he already has one of them, unencrypted. My question ...
0
votes
1answer
41 views

Bilinear map + commitment

Let $\mathbb{G}_1,\mathbb{G}_2,\mathbb{G}_T$ be yclic group of the same order and $ e: \mathbb{G}_1 \times \mathbb{G}_2\rightarrow \mathbb{G}_T$, such that $u\in \mathbb{G}_1, g \in \mathbb{G}_2, ...
0
votes
1answer
28 views

Are more S boxes more secure in a SP-Network?

The classic DES uses 8 different fixed S boxes. If computer memory was not an issue, would say 800 different S boxes be more secure? I'm thinking of a SP-network that would only run on a server like ...
0
votes
3answers
50 views

Is the Salsa20/ChaCha20 keystream generation one-way?

Is it possible to recompute the Salsa20 or ChaCha20 key in a realistic time if the keystream and the nonce are given to an attacker? Or is the keystream generation one-way, like a cryptographic has ...
0
votes
0answers
24 views

GMAC implementation in C [on hold]

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
43 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 ...
1
vote
1answer
38 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
46 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
28 views

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

Let us consider the private key (5,7) how is this converted into a RSA public key file such as : ...
0
votes
0answers
17 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
18 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 ...
2
votes
1answer
45 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
29 views

Software applications to learn cryptography [on hold]

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
1answer
66 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 ...
6
votes
1answer
57 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
32 views

Creating of finite field over small prime number for Elliptic Curve [on hold]

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
80 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 ...
5
votes
1answer
70 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
34 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
14 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 ...
9
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 ...
2
votes
1answer
32 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
53 views

El Gamal Decryption with Big Numbers [on hold]

I have a message encrypted in ElGamal. I was wanting help on how to decrypt it. Here is the data that I was given: p value g value h value x value y value c value How would I go about doing this. ...
2
votes
1answer
145 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
44 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
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 ...
-3
votes
0answers
27 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
17 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
20 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
52 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
74 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
21 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 ...
2
votes
1answer
52 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
31 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
55 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
50 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 ...
4
votes
0answers
64 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
59 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
22 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
26 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
33 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 ...

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