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Can there be more than one valid private exponent for a given p, q, and e in RSA encryption?

For example, given: p = 173, q = 149, e = 3 Using phi(n) gives d = 16971 While using lambda(n) gives d = 4243 Both values satisfy the checking equation (de)%phi=1, so are both correct, and if so, ...
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1answer
24 views

How does re-hashing affects security strength?

I am currently saving hashed passwords for my website. Passwords are salted and then hashed using SHA3-512. I understand the security level of SHA3-512, as it is for all Keccak algorithms, is half the ...
5
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3answers
881 views

Why do people criticize and mistrust the e-voting based block chain?

I am planning to implement an e-voting system based on hyperledger fabric blockchain, however, I came across many criticisms from well-known security experts like Josh Benaloh and others. The problem ...
-2
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0answers
45 views

why after saving File becomes larger? Steganography [closed]

274534d7d1780203956040e16a2fd8712e21596c92d7ac2ecd959d0166f8a501 I am trying to solve this puzzle. Source program is unknown. However after saving the file from editor it becomes larger than original....
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0answers
19 views

Anonymous location hashing

Is it possible to know if two geographic locations are within a certain distance of each other without revealing the location? I'm thinking about contact tracing during the COVID-19 outbreak. ...
2
votes
1answer
34 views

Extract adversary's secret input in simulation based security proofs

I am trying to understand the simulation-based security proofs (as well as the UC framework), I find that there is a basic assumption when proving the security, i.e., the simulator could extract the ...
0
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1answer
113 views

How to change the following commitment scheme to Pedersen commitment?

In my question here Zero knowledge set membership protocol The suggested solution allows a prover to choose a commitment $C$. Then, A trusted third party ($T$) can validate if $C$ is valid or not. ...
0
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1answer
17 views

Mac-sforge motivation for storing pairs

I don't understand why Q keeping pairs of instead of m like mac-forge solves the problem of generating a new tag on a previously authenticated message. Say, a previously authenticated message for "...
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2answers
59 views

Modes of operation that simply uses the tweak of a tweakable block cipher

What is the name of the mode in which we simply change the tweak for each block without the need for complex chaining modes? Is this mode secure? Are there any other recommended modes for native ...
1
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1answer
39 views

Message types in GPG

I am trying to check the part where messages are both encrypted and signed. But what is the difference between a message which looks like this ...
1
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1answer
20 views

Fully homomorphic encryption (over addition and multiplication) library in python

I was wondering if there is a commonly used library in Python (or another common language such as Java, C++, etc.) for fully homomorphic encryption over multiplication and addition that also supports ...
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0answers
24 views

Is it possible to “convert” to a curve

Assuming I have a 2 black boxes Box A: generates a private key and use it to sign whatever data I sent it (using secp256r1). It also returns the corresponding public key Box B: gets a public key, and ...
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0answers
22 views

I need help deciphering this [closed]

I'm not sure if this is the right place to ask this, but I need help deciphering this code. Message is as follows: "I,Zdg F\ух|Rю.DpьфоF}"rxVдrGGMjWяьеmqлiWaюeBseцюagаmьFsa-j|=d,фgdмeZvйwfmHlArцxπ"...
1
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0answers
19 views

CSPRNG unique seeds and proving uniform output

I have two related questions concerning cryptographically secure pseudo random number generators. My first question is as follows: are there conditions on the definition of cryptographically secure ...
2
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0answers
26 views

Provably secure way of expanding permutations

Gimli is a 384-bit permutation which makes use of an internal 96-bit permutation which works on columns. Every 4 rounds starting from the 1st a "small swap" is performed and every 4 rounds starting ...
0
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3answers
107 views

Why did the NSA create SHA?

new to cryptography, i'm trying to learn the program veracrypt, and i'm now trying to understand the history of hash functions and how it applies to veracrypt. so this is what i understand so far, ...
1
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2answers
289 views

Why is Math.floor(Math.random()*9000) not secure in JavaScript?

I heard that one can predict the output from Math.Random() of JavaScript, but another day I had an idea to combine Math.random() ...
2
votes
1answer
39 views

SHA-256 security for initial 32 bits

I have concerns regarding truncated SHA-256 hashes in an application I am building at the moment: Nomenclature secret - the full 256-bit SHA-256 result of hashing ...
1
vote
4answers
158 views

Why are there standards of encryption?

Pardon me if this question seems a bit obvious, but if someone has a key to your encryption, knowing what type of encryption you are using (or running outputs against a lot of common encryption types) ...
0
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2answers
109 views

Why is Curve25519 mostly used for key exchange?

When i studied the Applications where Curve25519 is used, i found out, that it is mostly used for the key exchange. Examples are the Signal Protocol and Threema. I know, that Curve25519 has a pretty ...
0
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1answer
63 views

Are bijective polynomials of degree $2 \bmod 2^m$ efficiently inverted?

Take a bijective polynomial of degree $2 \bmod 2^{64}$ like: $m = (n(n+1)/2)\ \bmod 2^{64}$ It is bijective and can trivially be inverted for numbers up to $2^{32}$ by calculating $\lfloor\sqrt{2m}\...
0
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1answer
28 views

ECDH Public Key Recovery - Determine if valid key exists from just signature and message

If I have just the (r,s,v) values of the signature and the message hash, what is the most efficient way to determine if a valid public key exists? I do not need to know the public key, just that the ...
0
votes
1answer
32 views

How can I get VMAC Code in pure c?

I had find a paper about VMAC algorithm:VMAC: Message Authentication Code using Universal Hashing. Now I want to implement this algorithm, But i don't find test vectors about it. Who can give some ...
0
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0answers
35 views

Is XChacha20 - Poly1305 Quantum resistant?

This is a question just out of curiosity, as I am a newbie to Post Quantum Cryptography. I have read several articles where they emphasize that current standardised symmetric encryption algorithms (...
0
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1answer
31 views

Example of a Two-party GMW Protocol

I have been looking for a concrete example of GMW protocol for two parties. I was trying with the following example for computing $XOR$ of two parties: A's secret bit is $a = 0$, B's secret bit is $b ...
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2answers
126 views

Chosen plain-text Attack on DES-X with roughly $2^{64}$ DES operations

Here is the quote from P. Rogaway,The security of DESX "the effective key length of DESX with respect to key search is at least 55 + 63 - lg(m) bits" where m is the number of chosen plaintext/...
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2answers
122 views

Is there an efficient algorithm that allows to construct a cryptographically secure $n$-bit hash function based on two unkeyed $n$-bit permutations?

Let $f(x)$ and $g(x)$ denote two independent, “ideal”, unkeyed, public $n$-bit permutations (two publicly known bijective functions that produce $n$-bit outputs from $n$-bit inputs), where $n$ is an ...
0
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1answer
48 views

How modern messengers encryption keys can't be hacked

I dont know is this question more like reverse-engineering or cryptographic. Why governments are hunting for encryptions keys? Aren't they delievering by the network the same as the encypted messages? ...
1
vote
1answer
335 views

Prove that function G is not a pseudo-random generator

I'm trying to do the following assignment: Let $G:\{0,1\}^n \rightarrow \{0,1\}^{n+1}$ and $G':\{0,1\}^n \rightarrow \{0,1\}^{n+2}$ be two pseudorandom generators. Prove that the function $G'':\{...
7
votes
3answers
4k views

Can curve25519 keys be used with ed25519 keys?

Can curve25519 keys be used with ed25519? I'd prefer to use ed25519, but there isn't a fast java version. For my application, I'd like to use curve25519 until I can get a faster ed25519 for java. ...
1
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1answer
68 views

Curve25519 key exchange in detail

So I'm trying to understand how the key exchange with Curve25519 works. I read the original Paper from Bernstein "Curve25519: new Diffie-Hellman speed records", but I still got some questions. First ...
3
votes
1answer
4k views

How Secure is gpg Command Using Symmetric AES-256 From Being Cracked

How secure is any data encrypted using the following command: gpg -o *encrypted_output_file_name* --symmetric --cipher-algo AES256 *file_to_be_encrypted* Can ...
1
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1answer
32 views

Computationally expensive key derivation whose difficulty is asymmetric

I am looking for a primitive or a construction that meets the following requirements. Is such a construction (a) theoretically possible, and (b) in existence right now? Given are: a long secret $X$ ...
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0answers
11 views

What is the probability to get all qubits as zeros with input of zeroes qubits [migrated]

question from exam: Bob built a quantum computer of 10 qubits. all qubits are set to zeroes. Bob performed on the system quantum fourier transform and then measured the system. what is the probability ...
-4
votes
1answer
51 views

I'm new to cryptography, why did cryptography in general, make cryptographic hash functions? [closed]

i'm new to cryptography, and i'm currently learning the open source program veracrypt, and as a complete normie, i felt like i should ask, why did cryptography create cryptographic hash functions? ...
3
votes
1answer
41 views

If I allow arbitrary initial hash values for SHA-256, what would be the weaknesses?

The initial hash values (IV) of SHA256 are fixed. However, let's say I modify the SHA256 hash function to allow the attacker to use arbitrary IVs rather than fixed IVs. What kind of weaknesses would ...
1
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0answers
26 views

Tracking Spread of CoV-19 along Social Graph while Protecting Privacy and Anonymity

In several countries there are currently ideas to track the spread of HCoV-19 by use of mobile location data. A good knowledge of the virus' spread throughout communities and countries will certainly ...
1
vote
1answer
28 views

How to calculate the redundancy of a language

I originally asked this question on the information security stack exchange but I think it's better suited here. I'm trying to calculating the unicity distance for a cipher applied to a language I ...
0
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0answers
24 views

Prove linkage between secret keys

Hey guys I'm not a crypto expert so apologies if the question is especially noobish. We have a web application that requires the user to sign certain messages. We have been storing the secret key in ...
8
votes
1answer
187 views

Most influential/illuminating papers/books/courses on lattice based cryptography?

I'm interested in some sort of "compendium" on lattice-based crypto. There are a bunch of maths behind FALCON and other stuff. A lot of articles are devoted to lattice crypto, but not of them are of ...
0
votes
2answers
38 views

set of integers modulo an integer q in lattice

Some literature about lattices set $\mathbb{Z}_{q}$ in $[-\frac{q}{2}, \frac{q}{2})\cap \mathbb{Z}$ but not $[0,q-1]$ such as "lattice signatures without trapdoors" and "lattice based blind ...
0
votes
0answers
24 views

Encrypt and decrypt data accessible by two users on the web on multiple devices

I am currently building a website where a user will be able to upload a file to my server and another user will be able to download the file. Now i want to add encryption to this with the following ...
0
votes
2answers
54 views

How is asymmetric cryptography safe if one of the keys is public?

Let's suppose $A$ is sending a message $m$ to $B$ using asymmetric cryptography. To guarantee the authenticity of a message, $A$ encrypts $m$ with $A$'s private key: $E(m, k_A) = m_A$. Then, $A$ ...
0
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0answers
15 views

Does every 256 bit number have a distinct sha256 result? [duplicate]

If I were some how able to create a table of all 256 bit inputs and outputs of sha256, would each of the inputs have a distinct output?
-1
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1answer
26 views

how we can display each round of PRESENT algorithm

how i can display each round of PRESENT algorithm knowing that i'm using the code c and i'm using a Key: 00000000000000000000 (80-bit)
0
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0answers
9 views

How to store private keys in browsers after Apple's decision to wipe script-writeable storage? [migrated]

We have a web application that puts a private key in LocalStorage, which enables users to sign off certain messages. It's been working fine until today we saw this announcement from Apple, https://...
0
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1answer
58 views

How to reduce Computational Diffie–Hellman problem and Decisional Diffie–Hellman problem to Discrete logarithm problem

I'm supposed make some reductions but don't even know where to start. Any help would or explanation on how to do this would be much appreciated.
1
vote
1answer
42 views

Can any part of AES encrypted blocks be used as PRFed value?

Suppose we need a PRF whose output space is 255bit. Then, what I can do with AES with 128-bit security is producing 2 AES blocks that are of 256-bit. Then, I will remove the most significant bit of ...
1
vote
1answer
231 views

Encryption: am I doing it right?

I'm trying to get a per-user encryption key scheme off the ground and need some validation from wiser crypto pros. Consider the following procedure: User provides registration information to include ...
0
votes
1answer
57 views

Security of key bits under indistinguishability for randomized encryption

My question is about symmetric randomized encryption. Let c=E(k,m,r) be a randomized block encryption function where r denotes a random input chosen for each message block m. k and c denote the ...

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