1
vote
1answer
15 views

Formal relationship between encryption and random number generators?

Cryptographically secure random number generators seem to have similar properties to symmetric encryption: initial seed is permuted to produce a random numbers (key and ciphertext) given the seed, ...
1
vote
1answer
27 views

How to implement homomorphic multiplication for Elgamal?

I want to add the homomorphic property to Elgamal in libgcrypt. This is the core code I added to the library. ...
2
votes
1answer
41 views

Committing Bilinear equation in Groth-Sahai framework

Groth-Sahai framework enables us to commit to QE, MSME, PP equations. Now, is the equation below committable in GS framework? A bilinear map $e: G_1 \times G_2 \rightarrow G_T$. $g_1 \in G_1$ and ...
-1
votes
0answers
7 views

Generating a code from package name of android apps

Consider an application which generates a long code from package name of applications. For example: ...
2
votes
1answer
65 views

How to use ElGamal to encrypt zero?

ElGamal encryption algorithm is as follows: To encrypt a value $m$, it chooses a random value $r$, and calculates $c_1=g^r$ $mod$ $q$ $c_2=m*h^r$ $mod$ $q$ where $g$ is the group generator, $x$ is ...
0
votes
0answers
9 views

Protecting a short password

I figured that a really secure password would be an AES 128 key. If this key were to be base 64 encoded, I could replace 4 random bytes in it in order to make it unusable unless you know which bytes ...
2
votes
1answer
95 views

Calculate the security of a cascade cipher

I’m reading “The Security of Multiple Encryption in the Ideal Cipher Model” and I’m having a hard time understanding something. How do I calculate the bounds of cascade cipher from the following ...
1
vote
1answer
87 views

To prove $r \cdot f_1 +f_2 \cdot (s+1)$ is secure

We define the polynomials $r, f_1,f_2,s \in R[x]$. Where $r$ is a random degree 1 polynomial and $s$ is a random polynomial such that: $degree(s)=degree(f_1)=degree(f_2)$, let $R$ be $\mathbb{Z}_p$ ...
1
vote
1answer
70 views

Are there signatures that don't have subliminal channels?

Are there signatures that don't have subliminal channels and also don't require commitments or zero-knowledge proofs? DSA or Shorr signatures need a nonce which can leak valuable information. There ...
1
vote
0answers
95 views

Ransomware RSA-1024 encrypted files [on hold]

Sorry if this is not the right place to ask this question, but it seemed most relevant to the Cryptography topic. One of the users on our domain was infected with a ransomware virus that caused all ...
1
vote
0answers
38 views

Signature verification with only hash (without full data)

I am looking for a way to sign a file, such that someone else can verify that I had this file, even if they only know a hash. I want to prove that I have the full file to someone who only has the ...
1
vote
1answer
22 views

what are the plaintext's for the RC4 stream cipher test vectors in RFC6229?

https://tools.ietf.org/html/rfc6229 has stuff like this: ...
-1
votes
0answers
48 views

how can I understand nonlinear coding for error detection

I want to understand how nonlinear coding can detect the errors in cryptography computing . actually I don't know what these code doing and what are the codewords in this system. now can any body ...
1
vote
0answers
33 views

What is the fixed point attribute of DES (when used with weak-keys)

I've heard in some lecture that the weak keys in DES implies the existence of $2^{32}$ fixed points in the algorithm, i.e. that $DES_k(x)=x$ for $2^{32}$ such $x$'s. I couldn't find anything about ...
1
vote
0answers
36 views

The purpose of the final xor in Davies–Meyer scheme [duplicate]

In Davies–Meyer hash construction scheme each block is xor'ed with the previous block cipher text. Why? The only obvious flaw I see in a scheme without this xor is the possibility to reconstruct a ...
0
votes
0answers
34 views

vector space retrieval model

In tf-idf weighting scheme of vector space model, weight matrix is calculated as a product of term frequency(tf) and inverse domain frequency(idf). I need paillier dot product calculation here. Can ...
2
votes
1answer
51 views

Security of DES P_BOX

I'm curious about the design of the P_BOX of DES. I found a paper on this topic, but it dates back to 1989. This means the effect of p-box values of the cipher immunity against Differential ...
1
vote
1answer
68 views

Attacker in a key exchange

I'm having trouble with the following question: $X(A) \rightarrow B:(A,N_X)$ $B \rightarrow X(S):(B,((A,N_X,T_B),K_{BS}),N_B)$ $X(A) \rightarrow B:(((A,N_X,T_B),K_{BS}),(N_B,N_X))$ ...
3
votes
2answers
139 views

Does RSA operate over a Finite Field (Galois Field)?

Is it correct to say that RSA operates over a Finite Field (Galois Field)? In this case GF(p)? I do understant that the modulo in RSA is not itself a prime number, but all the operations ...
13
votes
4answers
295 views

Why are primes important for encryption

Why are primes so important? Why can't we just use a random number? My guess is that it's because finding a random prime require more computing power, than finding a random number. Can anybody confirm ...
3
votes
1answer
157 views

Can keys from Bitcoin's Hierarchical Deterministic Wallets be correlated (reducing privacy)?

I'm trying to understand if the feature "Hierarchical Deterministic Wallets" in Bitcoin allows for complete privacy of all derived keys, and if any of those keys can be associated with each other ...
2
votes
1answer
51 views

How do we find the subkey out of a differential cryptanalysis?

I understand the differential cryptanalysis up to the "finding the last subkey" part. If XORing with the key doesn't change the differentials, how can testing different key affect the equations we ...
0
votes
0answers
28 views

Memory requirement in light weight block ciphers cryptanalysis

If we have a light weight block cipher where the block length is different than the key length. Let's say the block has a length of 64 bits while the key is 80 bits. For an attack to be successful, ...
1
vote
2answers
147 views

why $e(g,g)^N=1$ in bilinear pairings holds?

I can't get the point of prime order bilinear pairings:$\mathbb{G}\times\mathbb{G}\rightarrow\mathbb{G}_T$,$g=$ generator of $\mathbb{G}$ , $N=p*q$, $p$ and $q$ primes and $e(g,g)^N=1$. why ...
1
vote
2answers
81 views

Group description in pairing based cryptography

Suppose we have a public key encryption scheme, in which public parameter contains $(p, G, G_t, e, g)$, where $p$ is prime number, $G$ is a (cyclic) group of prime order, $e:G \times G \mapsto G_t$. ...
1
vote
1answer
63 views

Polynomial division hardware implementation

I am beginning the implementation of the polynomial binary division algorithm now as I understood i will be checking the MSB bit if 1 to XOR and shift the sum if 0 i will only shift. What I am not ...
0
votes
0answers
9 views

How does SafeNet MobilePass calculate the counter for following passwords?

Original Question: How does SafeNet MobilePASS generate passwords? The algorithm to calculate passwords was implemented by the author of the original question here: ...
1
vote
1answer
23 views

How does SafeNet MobilePASS generate passwords? (TOTP Variant)

This question is similar to How does SafeNet MobilePASS generate passwords? The question and answer there is related to the HMAC Variant of SafeNet Mobilepass. I'm looking for details on the TOTP ...
2
votes
1answer
261 views

Finding a collision for a hash function

I'm trying to find a collision for the following (modified) Merkle–Damgård hash function. Suppose we already have a hash function $h : \mathbb{Z}_2^{2·n} \to \mathbb{Z}_2^n$ for fixed length bit ...
2
votes
1answer
148 views

SHA-1 collision resistance

I'm researching on the SHA-1 algorithm and looking for reasons why it has fallen prey to differential cryptanalysis. I have read the research papers by Merc Stevens and Wang both of which describe how ...
1
vote
1answer
85 views

Is it safe to AES-CBC and AES-CMAC both using the same key?

There is a very similar question (Using a derived key for CMAC) but it doesn't quite answer this one (at least for me it does not). I have a situation where I need to transfer some data. My data has ...
1
vote
1answer
75 views

one time pad regarding

If I had two ciphertexts $$c_1 = m_1 \oplus y_1 \text{ and } c_2 = m_2 \oplus y_2$$ will it be possible to obtain $$z_1= (m_1 \lor m_2) \oplus y_1 \oplus y_2 \text{ and } z_2= (m_1 \land m_2) ...
2
votes
1answer
58 views

Secure multiparty computation of conjunction

Suppose Alice and Bob each have bits a and b, respectively. How can Alice and Bob compute the function ...
2
votes
1answer
50 views

Build set with PKI from reliable broadcast / random beacon

I am trying to build a protocol (or find an existing one) for creating a set $S_2$ with PKI from a set of parties $S_1$ that initially does not know anything about the other parties. We assume ...
12
votes
0answers
222 views
+50

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 ...
1
vote
1answer
49 views

Perfect secrecy of a crypto system

Suppose we have the following crypto system: $P = C = K = \{0, 1, . . . , n − 1\}$, $E_k(x) = (x + k) \bmod n$ and $D_k(y) = (y − k) \bmod n$. Prove that the crytosystem has perfect secrecy. Perfect ...
2
votes
1answer
55 views

Possible hashing scheme

Plaintext(binary) : 10101100 //very short for easy understanding Suppose we have 4 predefined schemes/functions, rotate (101 -> 011) flip (1101 -> 1011) exchange (11011 -> 10111) stretch (1100 -> ...
0
votes
2answers
155 views

What would be the best plain text Cryptography method without the use of a computer? [closed]

What would be the best Cryptography method without the use of a computer? This could be a list of the current options available, that could be used without the use of a computer ...
4
votes
1answer
91 views

Dancing confusion with Daniel J. Bernstein's stream ciphers

I know of Salsa20 which won the ESTREAM competition. This is dated of 25 Dec 2007. There is also the ChaCha20 stream cipher (cr.yp.to/chacha.html). This claims to increase the amount of diffusion ...
1
vote
1answer
137 views

fully homomorphic encryption (FHE)

Please, I would like to find some hints or solution to my following problem, I would appreciate your assistance to walk with me throughout the solution Given fully homomorphic encryption (FHE) ...
7
votes
1answer
150 views

Why is authenticated CFB mode insecure?

I read that the following adaptation of the CFB block cipher mode into an authenticated mode is prone to chosen plaintext attacks, yet Im still unsure how to prove it: Let $P_1,P_2,\ldots P_n$ be the ...
1
vote
0answers
87 views

How represent message in Menezes–Vanstone elliptic curve cryptography

I ask about represent message in Menezes–Vanstone elliptic curve cryptography I now encrypt function as follow $C_1 = (M_1 * K_1) mod\ P$ $C_2=(M2 * k_2) mod\ P$ My question is about how much the ...
1
vote
1answer
99 views

Block cipher to encrypt 8 bytes/64 bits - Use 64 or 128 bit cipher?

Here's the problem: I have a transport stream that I have been requested to encrypt between the transmitter and receiver. The data size is at most 8 bytes so it seems I can only use ECB as I only have ...
0
votes
1answer
62 views

“Kernel attack” on MinRank — why do we guess $\left\lceil \frac k n \right\rceil$ vectors?

The kernel attack on MinRank is described here (page 5). My question refers to this line: Note that if $m = \left\lceil \frac k n \right\rceil$, the system essentially has only one solution ...
-2
votes
0answers
45 views

Encryption key input by a user [on hold]

I was looking for some research papers where the security scheme is using 'user input' key method (but could not find). I mean, some approaches where user will be the one who will put keys for ...
4
votes
2answers
208 views

Extending pseudorandom generator by one bit using exclusive-or of previous bits

Is it possible to have a pseudorandom generator that extends its output by 1 bit by simply appending the exclusive-or of all the previous bits? I know the output of a pseudorandom generator is ...
0
votes
0answers
5 views

How to replicate GPA's Sign and Compress option on command line in Windows [migrated]

As the title says, I need to replicate GPA's "Sign and Compress" option on the command line. I'm trying to automate some encryption of files for submission to a bank and the instructions they gave me ...
5
votes
2answers
262 views

Shannon confusion and diffusion concept

I read the document(not the whole document) from Shannon where he speaks about the concepts of confusion and diffusion. I read in many places(not in the document but around the internet) that ...
5
votes
3answers
382 views

What is the difference between uniformly and at random in crypto definitions?

Very often in the description and analysis of a cryptographic protocol there is a need for a an element $k$ that is sampled uniformly AND at random. Is there a redundancy in the definition with ...

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