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IS F is PRG or not? [closed]

Let $G$ be a PRG and let $F$ run $G$ and output its bits in reverse. Is $F$ is PRG? If yes give proof otherwise give a counter-example.
vignesh4999's user avatar
0 votes
0 answers
21 views

Prove variable length MAC scheme is insecure

I have to prove the following variable length MAC scheme is insecure. Im not really sure how to approach this problem. Although I know the problem with this scheme is the fact that it is variable ...
Jaxon Steinhower's user avatar
0 votes
0 answers
47 views

Prove fixed length MAC scheme is insecure

I have to prove the following fixed length MAC scheme is insecure. Im not really sure how to approach this problem. Although I do know that for this specific problem keeping one of the blocks the same ...
Jaxon Steinhower's user avatar
0 votes
0 answers
22 views

what is the difference between a hash function and a digest algorithm? [duplicate]

i know that digest is the ouput obtained from a hash function as well as from digest algorithm so does that mean hash function and digest algorithm are same?
Manish kumar sinha's user avatar
1 vote
0 answers
54 views

Relating the noisy data to it's associated original/actual one

We have a set of query answers, i.e., $A = \{A_1, A_2, \dots, A_m\}$ and then we add noise to each of $A_i$ using a mechanism ($M$) providing differential privacy, i.e., $M(A_i) = O_i$. We denote the ...
Amirhossein Adavoudi's user avatar
0 votes
1 answer
43 views

Is there a way to defeat statistical information leak in Vigenère cipher when the ciphertext is reasonably larger than the key size?

I read in this answer here that if the ciphertext is reasonably larger than the key size, Vigenère cipher is easily breakable. Is there a way to repeat the key if it is reasonably smaller that the ...
alpominth's user avatar
  • 393
0 votes
0 answers
27 views

Proof for embedded composition of PRG's

I have two secure pseudorandom generators, $G_1 : S\rightarrow R, G_2 : R\rightarrow T$. Now I need to prove that the PRG $G_3(s) = G_2(G_1(s))$ is secure. I figured that I would construct two ...
Izzy Handkammer's user avatar
0 votes
0 answers
28 views

Cryptographic Proof of Showing A Construction of PRGs is Also A PRG [closed]

Let G : {0,1}n → {0,1}2n be a PRG (for every n), and let s ∈ {0,1}n. Prove that the following construction is NOT a secure PRG. Gd(s): first run G(s) = x||y (where |x| = |y| = n−bits). Then run G(y) = ...
sangaCat's user avatar
0 votes
1 answer
28 views

If the truncation function provides differential privacy

We have values in the range $[a, b]$, and we apply a differential privacy mechanism to add noise to these values. After obtaining the noisy values, we employ the following truncation function: if a ...
Amirhossein Adavoudi's user avatar
0 votes
0 answers
37 views

family of hash functions in ring signature

Some kind of cryptographic hash function H(x) is given. Is it true (under what assumptions?) that the family H_i(x) = H(i||x) ...
pes oves's user avatar
2 votes
2 answers
589 views

What are advantages of chaos based image encryption methods over simply treating images as opaque bit strings?

For an exercise at uni I am tasked with optimizing the execution speed a chaos based image encryption algorithm 1. While I have taken an introductory class to information security, I never came ...
förschter's user avatar
0 votes
0 answers
18 views

IS this scheme secure (private P[M =m | C =c] = P[M=m] and correct P[m =m']) [closed]

Message space = {1,2} Key Space = {1,2,3,4} Cipher Space = {1,2,3} M * K = C So the relations are: 1 * 1 = 1 , 2 * 1 = 2 ,1 * 2 = 2 , 2 * 2 = 1 ,1 * 3 = 3 ,2 * 3 = 1 ,1 * 4 = 1 , 2 * 4 = 3 Thanks
Awesomeman123's user avatar
0 votes
1 answer
43 views

Is this an example of a sponge construction?

I am having difficulties understanding a sponge construction, as I don't really understand whether the long internal state of a sponge construction is compressed in the squeeze phase, or whether bits ...
RA35's user avatar
  • 13
1 vote
1 answer
36 views

What is the difference between Shamir secret sharing and additive sharing?

When it comes to applications, such as multiplication or addition, is there any difference between Shamir secret sharing and additive secret sharing?
Gink Lober's user avatar
-1 votes
0 answers
15 views

Expected data is incorrect when scalar_mul_size is different from the modulus size in ECC MUL [closed]

Does that when the scalar_mul_size was different from the modulus_mul_size this impact on the output data?
amjed ghrairi's user avatar
0 votes
0 answers
33 views

How to calculate Cardinality of an Elliptic curve over $\mathbb Z_{23}$

How to calculate Cardinality of an Elliptic curve over $\mathbb Z_{23}$. $E: y^2 = x^3 + x + 1$ defined over $\mathbb Z_{23}$.
Sanjai Kumar's user avatar
0 votes
0 answers
49 views

Is the One-Time-Pad IND-CCA2 Secure?

I know that the OTP is considered to have perfect secrecy, but I haven't seen anything about its security against chosen ciphertext attacks, and I was wondering about its secrecy in this regard. My ...
chemN00b's user avatar
  • 113
0 votes
0 answers
63 views

What is the fastest 128-bit non-cryptographic hash function?

I need a 128-bit hash function which is extremely fast since it will be used for generating unique IDs for billions of objects. It doesn't need to be a cryptographic hash function nor does it have to ...
TypicalHog's user avatar
0 votes
0 answers
47 views

Universal Family of hash functions [closed]

Some kind of hash function H(x) cryptographic is given. Is it true (under what assumptions?) that the family H_i(x) = H(i||x) is ...
pes oves's user avatar
0 votes
1 answer
24 views

Is it possible to calculate key(0) and key(1) of ZipCrypto using key(2)?

Here is Zipcrypto decryption algorithm: ...
terry franklin's user avatar
1 vote
1 answer
92 views

Ring Learning With Errors : why is it called ring and referred it as Ring LWE

I am curious about the structure of the quotient ring in Ring LWE. So $R=\mathbb Z[x]/(x^n+1)$, where $x^n+1$ is an irreducible polynomial and $n$ is a power of 2. So, this structure would not be a ...
user479610's user avatar
1 vote
1 answer
70 views

Ring-LWE lattice cryptography and FFT Trick for $X^n+1$

in reference here the FFT trick for $X^n+1$ is discussed with reference to the Number Theoretic transformation. On page 5, the Chinese Remainder Theorem is used to define the mapping. So far so good. ...
TreeBook1's user avatar
0 votes
0 answers
36 views

Blob for Commitments

I am currently reading the paper Multiparty Unconditional Secure Protocols (https://dl.acm.org/doi/10.1145/62212.62214). They use blob for commitments. The purpose of blobs is to allow a participant $...
Novice_researcher's user avatar
3 votes
1 answer
64 views

How to reconstruct low order bits of $t$ of CRYSTALS-Dilithium from a small number of signatures?

In FIPS 204 (https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.204.ipd.pdf): "The vector $\textbf{t}$ is compressed in the actual public key by dropping the $d$ least significant bits from each ...
Jong Hyeok Lee's user avatar
0 votes
0 answers
40 views

How to calculate inverse of scalar product using secret sharing

Following a question about calculating the inverse value among two parties, I want to ask about the possibility of getting an inverse of the scalar product (|I|. |J|) that is part of the computation ...
ShokofehVS's user avatar
1 vote
1 answer
136 views

Encrypting the nonce in AES-CCM

I'm working on a network where nodes communicate using AES-CCM encryption, within a context of tight bandwidth limitations, making every bit count. The setup uses a nonce that combines a 16-bit node ...
byte-carlton's user avatar
1 vote
1 answer
203 views

ChaCha20 as a block cipher

Would it be possible to use ChaCha20 as a block cipher? With the key, the entire block function can be reversed.
SomeHybrid's user avatar
2 votes
1 answer
185 views

Can we use several times the same RSA and ECC keys?

For RSA or elliptic cryptography, can we use the same public/private keys for several exchanges, or is that unsafe? Does it lower the security of the protocol? To me it doesn't matter, as receiving ...
Wheatley's user avatar
  • 145
0 votes
1 answer
105 views

Clarifying terms for cipher, algorithm, rsa, asymmetric, openssl

I am a self taught front-end developer and I am just trying to get my cryptography terminologies straight. I will make some statements. Can someone correct my mistakes? Question 1 I read that cipher ...
learningtech's user avatar
2 votes
2 answers
314 views

Is it possible to create a mix of predefined and generated shares for Shamir's Secret Sharing?

In standard Shamir's Secret Sharing schemes the shares are generated from randomly generated polynomials. I was wandering if it would be possible to create some predefined shares that a user would be ...
Euan's user avatar
  • 21
1 vote
1 answer
166 views

Brute force against DES

Let a plain text message M be DES encrypted with two different keys (K1 and K2) to produce ...
Jib's user avatar
  • 113
0 votes
0 answers
28 views

The parameters in TLS1.2 server signature with ECDSA

I'm trying to write a webserver. I'm using TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 (secp256r1). I generated a CA certificate using OpenSSL (using prime256v1). I generated the hash using server_random +...
polipo09's user avatar
2 votes
0 answers
186 views
+50

How could a 1024‒bits RSA modulus be most economically factored within months today?

Of course this is a question with an answer that is due to evolve. A 2002 paper about TWIRL stated that the cost would be around 10M\$ and an other 10M\$ to manufacture the device. A later 2007 paper ...
user2284570's user avatar
0 votes
0 answers
58 views

El Gamal encryption variant and its security

We are given an El Gamal variant and are requested to find the decryption scheme and the security of the encryption. The variant operates on a group $\mathbb{G}$ of prime order q and g, h are two ...
Giorgos Mitropoulos's user avatar
0 votes
1 answer
39 views

Devising a system that allows for aggregate computations but does not hold the single values

First of all apologies if this is not the right place. I am not very knowledgeable in cryptography but I thought you can at least point me in the right direction of research. The following is a toy ...
Gianpiero Cea's user avatar
0 votes
0 answers
52 views

Multiplication of two Shamir Secret Shares

In Shamir Secret Sharing, I'm trying to figure out that how can I multiply a constant and shares with different mods (fields) and obtain the multiplication of this constant and secret? Assume ...
Semiramis's user avatar
2 votes
0 answers
50 views

Inefficient double-lengthening PRG

I'm trying to prove that an inefficient double-lengthening PRG exists, i.e. construct a PRG $G: \{0,1\}^n \rightarrow \{0,1\}^{2n}$ My current approach is to bound the number of poly-time non-uniform ...
Stevie's user avatar
  • 121
0 votes
0 answers
15 views

Aggregate Signatures Overview

I've been learning about aggregate signatures lately, are there any overviews or learning materials about aggregate signatures (including security properties)?
Ping Ping's user avatar
3 votes
2 answers
96 views

RSA given 30% MSB of p and 30%MSB of q

is factoring RSA given 30% MSB of p and 30%MSB of q possible in polynomial time? Notice that it is known that given 50% MSB of p or q it is doable in polynomial time using Coppersmith's theorem
Don Freecs's user avatar
0 votes
1 answer
52 views

Protocol for verifying novel compression algorithm?

By the pigeonhole principle, we can demonstrate that arbitrary lengths of random data are uncompressible in the general case. But let us imagine that I claim that I have created an oracle that can ...
johnwbyrd's user avatar
  • 101
-2 votes
0 answers
67 views

Missing Bitcoin bought 10 years, need help [closed]

I paid £10 to buy some bitcoins nearly 10 years ago and at that time there was no bitcoin wallet etc so I was given some codes which I have no complete clue what to do with. What made matter worse ...
CryptoClue's user avatar
2 votes
4 answers
163 views

Are there asymmetric encryption algorithms that preserve equality? Are they safe to use for data obfuscation?

I have a database table that needs to be shared between multiple parties. There is a sensitive column than must be obfuscated in a way that preserves equality relationships between records. A trusted ...
Erp12's user avatar
  • 123
0 votes
2 answers
93 views

Is it possible to perform reverse rsa encryption ? (using the public key for decrypting and the private key for encrypting)

Simple question, but I couldn’t find an answer as I know about signing but don’t want it. The aim would be to encrypt someone’s bet parameter as a short message using the private key and use the ...
user2284570's user avatar
15 votes
1 answer
1k views

Impact of Ryan and Heninger's CRYPTO 2023 paper on post quantum cryptosystems

From Schneier's blog, which seems to have been written in response to a somewhat recent Quanta magazine article: The winner of the Best Paper Award at CRYPTO this year (2023) was a significant ...
kodlu's user avatar
  • 22k
0 votes
0 answers
36 views

Proof that the DSA ID scheme is secure

I want to prove that the DSA identification scheme is secure and orientated me at the proof that Schnorr ID scheme is secure. In the book "Introduction to Modern Cryptography" by Katz, ...
Traubenzucker's user avatar
5 votes
1 answer
174 views
+500

Secret sharing thresold scheme with small shares

Shamir secret sharing1 is a common method to split an arbitrary secret (login credentials, symmetric or private key) between $n$ persons, so that a threshold of $k$ persons is required to rebuild the ...
fgrieu's user avatar
  • 140k
0 votes
0 answers
26 views

Lattices: Change output length from the input length

I am studying lattices and I would like to know if there exists a scheme that for a input length of the secret n it is possible to get a result of size 2^n for example without an adversary knowing?
Lattu's user avatar
  • 1
0 votes
1 answer
94 views

What exactly is RSA_WITH_AES256_CBC_SHA256?

Quick disclaimer, I am pretty new to cryptography. I only understand the basics of asymmetric and symmetric encryption. In particular, RSA and AES. I have a project where my service is receiving an ...
Aurelian Milleram's user avatar
0 votes
0 answers
35 views

Manual Calculation of Twofish [closed]

Is There an Opensource or paper that explain Manual Calculation of twofish. or someone can give me explanation how to mannualy encrypt with twofish algorithm for project. I have to do calculations ...
Rahman's user avatar
  • 1
0 votes
0 answers
127 views

Security of a scheme to prevent MitM in multi-AES

$$c_i'= AES_{128}(c_i,[i,k_i,0]) $$ $$k_i' = k_i \oplus c_i' \bmod 2^{60} $$ $$K_{i} = k_i' \cdot (c_i \oplus c_i') $$ $$c_{i+1} = AES_{256}(c_i',[i, k_i', K_{i}])$$ Those two AES operate each in ECB ...
J. Doe's user avatar
  • 573

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