Latest Crypto related questions

Score: 1
What kind of encryption is this?
fr flag

Hey can someone please tell me what kind of encryption this is? This is not the whole encrypted code but you should still be able to tell what it is from the structure.

HC1:6BFOXN*TS0BI$ZDFRH5+FPWF9EIZ.0769Y3S3XHP+56R5-F9/17BOMEY4/OBMMD/GPWBILC9GGBYPLR-SNH10EQ928GEQW2DVJ5UL8W2BM8Q.L8SNCYNAK+FA7E7:4N3IK/4S1ARO4R48/3987CGSK37F/HS$*S-CK9B92FF9B9LW4G%89-8CNNM3LK.GVD9O-OEF82E9GX8$G10QVGB3O1KO-OAGJM*KIE9MI ...

Score: 2
VDF / RSA groups
ar flag

I believe I am overthinking it; however, I need to clear out my doubts.

What is exactly RSA groups and how their order is unknown? I know in RSA N is computed by multiplying two prime numbers (p and q) and it is hard to find p and q given N. Is N what is called RSA group?

In VDF they use unknown order of RSA group; however, N is public.

Score: 0
Existential unforgabilty of a separately signed message
au flag

Assuming I have a valid signature scheme, and modify it like:

m = m0 || m1, and output Sign(sk, m0) || Sign(sk, m1).

While it is correct, would this violate existential unforgability?

Score: 0
opposite-people avatar
Private key encryption that is not CPA secure
br flag

I've been learning about different types of encryption schemes in class and I was wondering if it's possible to create a private-key encryption scheme that is multi-message secure but is NOT CPA-secure?

It seems that CPA security implies multi-message CPA security, but what about the other way? For example if given a private key multi-message secure scheme what changes would need to be made to ensure i ...

Score: 0
Novice_researcher avatar
LR Oracle for CPA Security for Multiple Encryption
br flag

How does LR Oracle model help achieve the CPA security for Multiple Encryption. I am not able to understand how LR oracle model gives an advantage over the normal encryption oracle.(Reference to Chapter 3 Katz).

Score: 1
Lavender avatar
Remote Attestation: when to use Checksum and when to use a Cryptographic Hash function?
in flag

In computer security applications, to check the integrity of a specific data/program binary, a cryptographic hash function is normally deployed to generate a digest and compare it with a reference digest.

When a remote device proves the integrity of the code and data residing on the platform to a verifying party, it is called remote attestation.

Looking into different remote attestation schemes, I r ...

Score: 0
How to know the exact result in Paillier cheaper-constant multiplication
de flag

The encryption function $E_{k^+}: Z_n \rightarrow Z_{n^2}$.
The decryption function $D_{k^-}: Z_{n^2} \rightarrow Z_n$.
$m_1 = 42, k = 15, n=77$.
After encryption, exponentiation and decryption, I get: $$D_{k^-}((E_{k^+}(m_1))^k) \equiv 14 \bmod 77$$ The class of residue of $14$ is of the form: $$\langle 14 \rangle = \{\alpha \in Z: 14 + \alpha*77\}$$ And one of these values is $630 = 14 + 8*77 \ ...

Score: 1
hambam avatar
Time complexity of a brute force attack on Shamir's Secret Sharing SSS
in flag

I have searched everywhere in academic papers about time complexity of a brute force attack on a Shamir's Secret Sharing key. I'm confused between if it is $O(p^k)$ or $O(p)$, such that $p$ is the modulo of encryption and $k-1$ is the degree of the encryption polynome. Because practically, if we're going to rebuild the polynome of encryption, it's equivalent to brute forcing all $p$ possible values for  ...

Score: 0
mazino avatar
An elliptical curve over GF(2^3) is defined as y^2+xy=x^3+ax^2+b with the given value of a= g^3 and b=1.R = P + Q, where P = (0, 1) and Q = (g^2, 1)
ke flag

An elliptical curve over $GF(2^3)$ is defined as $y^2+xy=x^3+ax^2+b$ with the given value of $a= g^3$ and $b=1$. $R = P + Q$, where $P = (0, 1)$ and $Q = (g^2, 1)$

Can someone solve this question using an elliptical curve cryptosystem? I have tried solving it but could not do it. I need to find R.

Formulas Used

GF Table

Score: 2
YHWang avatar
What do the "adversary state" and "internal coins" mean?
ru flag

I was reading papers about searchable symmetric encryption these days and in the security definition part the author mentioned:

where state is a polynomially bounded string that captures A1’s state, and the probability is taken over the internal coins of Keygen, A, and the underlying BuildIndex algorithm.

So what exactly do the "state" and "internal coins" mean?

Score: 0
jared chong avatar
How to use nonce, counter, and IV in AES-256-CTR?
id flag

preface: i am not cryptographically savvy. there are similar questions on this board but they do not give the answer i need.

how do i construct a valid IV, given a nonce? What does this have to do with a counter?

im doing 2-way communication with a bluetooth module (it is the server to my phone's client) and its data is encrypted using AES-256-CTR with a 32B key and a 128-bit (16B) counter. after succe ...

Score: 3
Tristan Nemoz avatar
How to build a periodic PRF from a PRF?
ru flag

This question may be related to this one, though the construction differs.

Let us consider a PRF $f$. We define $g_k$ as $g_k(x)=f(x)\oplus f(x\oplus k)$. Is $g_k$ a PRF, assuming $k$ is chosen at random?

I tried to prove this as follows. Let us consider an adversary $\mathcal{A}$ that is able to distinguish between $g_k$ and a PRF with non-negligible advantage. Let $\mathcal{R}$ be a reduction that has  ...

Score: 2
Tarick Welling avatar
Is this a valid AES instruction reordering?
nl flag

I'm trying to understand a verilog AES implementation. I know the order of the AES encryption steps to be as shown: enter image description here

However the code I see doesn't do this. They do the following flow graph: at the beginning of the encryption state is loaded with newstate or the plaintext. The round is set to max and is decremented each round.

They then do the following set of operations for each round until round ...

Score: 1
Ova Fleming avatar
How can I decrypt AES-256 GCM with key with a IV that is missing?
us flag

I want to decrypt a file that has been encrypted using AES-256 in GCM mode in libressl. I have the key but I don't have the IV, is there any way I can still decrypt?

Score: 1
Erfan Hosseini avatar
composition of RLWE distributions
cn flag

Assume we have the polynomial space $R_q$ defined as $R_q = Z_q/(X^n + 1)$. Additionally, we define the error distribution $\chi$ as a discrete centred Gaussian bounded by $B$. Let $s,t \in R_q$ be randomly selected secrets. Let $r_0=as+e_0$ where $a \gets R_q$ is selected uniformly at random and $e_0 \gets \chi$ is sampled from the noise distribution. We know that given $a$, the distribution of

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