All Questions
26,965
questions
-1
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Creating a Password Generator using CSPRNG in React JS
I am building a password generator website using ReactJS (link). I have read a lot about various ways of generating cryptographically secure passwords and I have decided to go with using CSPRNG. I don'...
1
vote
1
answer
23
views
Sending encrypted message without public key from recipient (elgamal)
assume Bob and Alice use Elgamal encryption scheme. Alice wants to send Bob a message, but does not know Bobs public key. Is there a way for Alice to find out Bobs public key by receiving multiple ...
- 11
1
vote
1
answer
21
views
How to crack sha256 used as streamcipher with known or guessable block
Using SHA-256 as a stream cipher appears to bear cryptographic weaknesses, however, I am not quite sure how to implement them in decryption.
Assume that I have an encryption function using 64-byte ...
- 13
1
vote
1
answer
38
views
How to create a key for AES in a 192 bit key length from a password?
Let's say that I have a password. And it's secure. But it's a 10-character string.
So If I wanted to create an AES key for the 128-bit version of the algorithm I would just hash it using MD5. Or If I ...
- 111
0
votes
0
answers
15
views
Has anyone come across any Papers on Statistical analysis of Present cipher? Nist or Dieharder
I need to Perform Statistical Analysis of Present. I choose NIST but I am getting underflow error even though I am taking 10 million bits.
0
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0
answers
9
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How to receive money via from another country via Trust Wallet? [closed]
My friend and I have a Trust Wallet, but haven’t used it before. How can he send some currency to my wallet? He lives in another country.
- 101
0
votes
0
answers
11
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How to import OpenPGP Card / YubiKey backup encryption key [migrated]
When I generate a new OpenPGP key on a YubiKey, it gives me the option to save a copy of the encryption key as a backup like so:
...
- 101
0
votes
0
answers
33
views
Diffie-Hellman: how to solve an alternative of Diffie-Hellman given an algorithm that solves Square Diffie-Hellman?
A simple question.
How can I proof the next polynomial reduction? : $DH’ ≤_{p} SQ$
where DH': given $g^{a}$ and $g^{b}$, compute {$g^{ab}$,$yg^{ab}$} where $y= g^{d/2}$, d is the order of cyclic ...
0
votes
0
answers
13
views
What, if any, are the IETF namespace notations for OpenPGP signatures?
RFC 4880 section 5.2.3.16, "Notation Data," describes how arbitrary additional notations in the form of name-value pairs can be included in an OpenPGP signature packet. Regarding names, it ...
- 101
1
vote
1
answer
35
views
Differential cryptanalysis - how to extend the attack to rounds before the last?
Suppose that we have a block cipher such that the last round of the cipher depends on half of the key and the penultimate round uses the other half.
Suppose also that I attacked the last round using ...
- 23
0
votes
1
answer
56
views
RSA not encrypting properly when e=d?
I'm trying to implement the RSA algorithm with some random (valid as far as I know) generated values but for this combination, encryption/decryption doesn't work.
...
- 103
0
votes
0
answers
35
views
Proving pairwise independence of a set of hash functions
A collection of hash functions $H=\{h:\{0,1\}^n \to \{0,1\}^m\}$ is pairwise independent if for every $x_1 \neq x_2 \in \{0,1\}^n$ and $y_1, y_2 \in \{0,1\}^m$:
$$ \Pr_{h \leftarrow H}[h(x_1)=y_1 \...
- 137
0
votes
0
answers
9
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Example of enhanced trapdoor perrmutation (Enhanced TDP)
I am currently reading about Trapdoor Permutations (TDP). While I can totally understand and think of examples of TDP. I cannot think of any examples of Enhanced TDP. The definition of both TDP and ...
- 268
0
votes
0
answers
12
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Calculate unique secrets of a hash algorithm, which produces a deterministic bit array of length 7
I can't really wrap my head around it. So given a hash algorithm which always produces a 12 bit array. How would I calculate the count of unique secrets with a collision rate of 75%.
- 1
0
votes
0
answers
36
views
Value to proving that breaking a cipher requires large amounts of plaintext
Is there any theoretical value to proving that a cipher cannot be quickly broken by any algorithm, unless that algorithm has some large number of plaintext ciphertext pairs (i.e. a number of plaintext/...
- 432
0
votes
1
answer
43
views
AES CBC: When to use new IV
I am trying to figure out when to use a new IV for an AES-CBC communication and whether my approach is safe.
Here is a quote from Thomas Pornin from a similar question:
So, to sum up: you must choose ...
- 135
3
votes
1
answer
77
views
What are not non-negligible functions?
I had a brief look at "On Defining Proofs of Knowledge" by Bellare and Goldreich and I am a little confused by their definitions.
I was under the impression a negligible function $f$ was ...
- 4,691
4
votes
0
answers
42
views
If a curve $E/\mathbb{F}_q$ is secure, what can be said about $E/\mathbb{F}_{q^2}$
Let $E$ be a known, "secure" curve, defined over a field $\mathbb{F}_q$ where $q$ is either a prime $\geq 5$ or a power of $2$. Denote by $n$ the amount of rational points of $E$.
Consider $...
- 51
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votes
2
answers
70
views
Isn't an asymmetric cipher (like RSA) algorithm sufficient for all basic needs, when speed is irrelevant?
Why I care: I want to implement some secure sessions for communicating over internet and since I am a complete amateur in this and don't want to spend a lot of time learning about cryptography or ...
- 113
1
vote
2
answers
98
views
Can a MITM during Diffie-Hellman key exchange manipulate both sides to generate symmetric secrets?
Is it possible for an attacker on a Diffie-Hellman key exchange to manipulate both sides in a way so that the secret generated on each side is identical?
Or put differently, would it be possible to ...
- 13
1
vote
1
answer
72
views
Σ-protocol that proves an even number was committed using Pedersen commitment scheme
I need to design a Σ-protocol ZKP using Pedersen commitment scheme that proves knowledge of a, y such that statement A = h^y * g^a only holds for even y (y=2x).
Of course, the protocol needs to be ...
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votes
1
answer
50
views
What is a ciphering key?
In Hebrew language there is the term tzophen (צופן) which means cipher.
There is also a term "maphtech hatzpana" (מפתח הצפנה) which means "ciphering key".
What is a ciphering key?
...
0
votes
1
answer
46
views
Question on notation of random variables in probability ensembles
Let's consider this definition of computational indistinguishability.
Computational indistinguishability. A probability ensemble $X=\{X(a, n)\}_{a \in\{0,1\}^{*} ; n \in \mathbb{N}}$ is an infinite ...
- 268
0
votes
0
answers
52
views
Attack against stream cipher (LFSR with ASCII)
I'm reading Understanding Cryptography by Christof Paar and Jan Pelzl. In chapter 2 (Stream Ciphers) there's a question that goes like this:
Assume we have a stream cipher whose period is quite short....
- 123
2
votes
1
answer
52
views
What are the key difference between Shannon entropy and Guessing Entropy?
Any body can explain, what are the key difference between Shannon entropy and Guessing Entropy? In some research I got entropy uses binary search or balanced huffman tree. Guesswork uses linier and ...
- 21
2
votes
1
answer
285
views
Security of equal discrete logs (over different bases)
I am trying to find a reduction for the following DLOG problem in generic groups. It is a simple generalization but I'm not finding any reference (the closest being the Chaum-Pedersen signature scheme ...
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-3
votes
0
answers
134
views
Give ordering as A<B<C<D by comparing MiMC,Poseidon, Pedersen and SHA256 in terms of Gas cost, capacity, proof generation efficiency, proof size [closed]
I need to compare the 4 hashing techniques-MiMC,Poseidon, Pedersen and SHA256 in four aspects gas cost, capacity, proof generation efficiency and proof size. Efficieny can be compared based on proven ...
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-2
votes
0
answers
34
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"After receiving the input and converting the unique value of each character stored in the plaintext into an integer m" Please let me know this part [closed]
1 Alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXTZabcdefghijklmnopqrstuvwxyz"
Each letter of the alphabet has a unique value, let's assume that it is assigned a number from 1 to 52 in order. therefore
...
- 1
2
votes
2
answers
52
views
What is the difference between AES-CCM8 mode and AES-CCM mode?
I know AES-GCM and AES-CCM but what is the difference between AES-CCM8 mode and AES-CCM mode ? Is it the length of the cipher?
- 19
0
votes
1
answer
54
views
Secure communication over insecure channel is based on the assumption of secure channel？
Consider a scenario：data owners $C$ sends a $l$ bits value $x$ to parties $P_0$ and $P_1$ via additively secret sharing scheme, for example, $C$ randomly selects $r \in_R \{0, 1\}^l$, and sends $r$ to ...
- 30
1
vote
1
answer
39
views
Do RSA powers of two modulus always have MSB set to one and so when DER encoded have 0x00 prefix?
Looking at https://crypto.stackexchange.com/a/30616/16548 and all the ways I generate RSA keys (code, SSL) the MSB is always 1 and so when DER encoded has 0x00 ...
- 147
0
votes
1
answer
44
views
Alternative to CBC mode encryption?
Given that CBC mode encryption is vulnerable to padding oracle attacks, what is the next best alternative ?
a) Include a hash check in the API scheme, validate the hash and then proceed with CBC. If ...
- 178
0
votes
0
answers
25
views
Simple scheme to publish data with a private key
The goal is for Alice to send an encrypted message to Bob. Neither Bob nor anyone else should be able to decode the message. Alice should be be able to decode it, when all data is shown to her. ...
- 101
0
votes
3
answers
70
views
Generalizing AES s-box circular shifts in bigger GF
According to wikipedia:
https://en.wikipedia.org/wiki/Rijndael_S-box
AES is doing interesting thing (where $<<<$ is circular shift):
$s = b \oplus (b \lll 1) \oplus (b \lll 2) \oplus (b \lll ...
- 805
0
votes
1
answer
23
views
AES GCM mode - what is ouput in that scheme?
I'm trying to understand that scheme:
https://xilinx.github.io/Vitis_Libraries/security/2019.2/guide_L1/internals/gcm.html
Here on page 11 it looks like GHASH gives only one value "Return $Y_m$&...
- 805
0
votes
0
answers
35
views
How to quantify privacy, when using homomorphic encryption?
How can you measure how secure or private the new variables are relative to the real (actual) variables.
I want to compare homomorphic encryption and differential privacy in combination with machine ...
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2
votes
1
answer
34
views
Validating AES GCM authentication tag between two different implementations
I'm a bit confused on how to validate the authentication tag between two different AES GCM implementations.
One implementation (on my part) is in Java. The other, I don't know.
In my implementation, ...
- 23
1
vote
0
answers
64
views
How fast is GHASH and what does it do?
I read here:
https://www.researchgate.net/publication/220335697_GCM_GHASH_and_Weak_Keys
how GHASH works. So we have $m$ 128-bit blocks $X_{i}$ and we compute in $GF(2^{128})$:
$Y_{m} = \sum_{i=1}^{m} ...
- 805
0
votes
1
answer
59
views
|RSA| Is it normal for $\phi(n)$ to work as RSA modulus?
So I was casually practicing RSA on paper for an exam, I did the whole process I wrote bellow, and when I tried the encryption and decryption I got distracted and instead of doing $m^e \mod n$
I did $...
- 1
0
votes
0
answers
39
views
What does it mean to break non-invertible stream cipher?
Let's consider for simplicity Middle-Square Weyl Sequence RNG:
https://arxiv.org/pdf/1704.00358.pdf
We can choose there parameter for independent stream generation, we can call it key. Let's consider ...
- 805
1
vote
1
answer
50
views
Hash of concatenated values (one public, one private)
Assume two end-points $A, B$. $A$ sends to $B$ a $Hash(pv||key)$, where $pv$ is a public value that can be intercepted by attackers. The $key$ is a common secure shared key in both end-points, and $||$...
- 303
1
vote
3
answers
82
views
Understanding public key in certificate precisely
Certificates are used very often in crypto. From the search, I am a bit confused what exactly is the "public key" inside a certificate essentially? Is it always a signature verification key, ...
- 113
1
vote
2
answers
73
views
Relative bits of security of slower functions
Leaving memory-hardness assumptions aside, some slow hash functions are iterated salted hash-chain versions of regular cryptographic hashes. This is usually defined by a ...
- 222
3
votes
1
answer
64
views
Is there any threshold-crypto library that is production-ready?
I am wondering if there is any available threshold crypto library that is well-audited and ready to be used in production.
Any pointer is appreciated.
2
votes
1
answer
56
views
Carry-less multiplication vs. multiplication in $GF(2^k)$
I implemented carry-less multiplciation using the CLMUL instruction set. This is similarly fast to simple modulo multiplication. But computating the result mod some polynomial is still very slow. I do ...
- 805
0
votes
1
answer
42
views
How to use symmetric encryption on 1on1 and group chat messenger?
Hi everyone so currently I'm trying to learn about encryption to build secure messaging app (Mobile-app, flutter based). I want the app to have 2 messaging features which are 1 on 1 messaging and ...
- 101
0
votes
0
answers
19
views
Unicity Distance redundancy clarification
I have an example of an exam question here:
The open message source is a language with an alphabet represented by an 8-bit ASCII code stored in a byte (=8 bits). The relative redundancy of the ...
2
votes
3
answers
552
views
NIST vs ISO Encryption standardisation process
skinny cipher has been lately considered as ISO/IEC standard while is still competing as building block of Romulus AEAD in NIST LWC finalists.
what is the difference between the two ISO and NIST ...
- 1,980
8
votes
2
answers
2k
views
On what Galois field AES really works?
I'm trying to understand the GF theory, but every time I come across information about AES it all makes no sense.
In my opinion $GF(2^8)$ defines any polynomial of the form:
$a_{7} x^7 + a_{6} x^6 + ...
- 805
1
vote
1
answer
43
views
Range proof for elgamal ciphertext
Alice has an ElGamal public key $y=g^x$. Bob encrypts a value $g^b$ based on Alice's Elgamal public key and he ends up with a ciphertext $(g^by^r, g^r)$. Can Bob prove that the value $b$ is in some ...