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Accidently deleted “~/.gnupg/pubring.kbx” , how to recover keys [migrated]

is there is any way to recover the encryption keys in this case, since they really important 1) the issue: i've lost my gpg key identifiers by deleting ...
0
votes
1answer
33 views

security parameter in lattice cryptography

In paper Lattice Signatures Without Trapdoors(Lyubashevsky2012), $n$ is the security parameter, why the authors set $n$ as 512 but not 80/100/112 to get 80-bit security/100-bit/112-bit security?
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2answers
92 views

Can an AES-GCM be cracked if the key is known but the nonce isn't?

I'm kind of new in this field and I've been trying to learn it. I'm now facing an issue where I have a couple of packages encrypted with AES-128 GCM and I have the key that was used to encrypt these ...
1
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2answers
62 views

How to backup a secret encrypted by multi parties without revealing the secret?

I'm searching for a way to backup a secret that only the end user knows the information with 2 trusted hosts. But trusted hosts shouldn't have access to secret at any time. First basic version : ...
0
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1answer
67 views

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, ...
1
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1answer
45 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 ...
1
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2answers
65 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
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0answers
136 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....
4
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3answers
971 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 ...
0
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0answers
29 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 ...
1
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2answers
60 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 ...
0
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1answer
23 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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0answers
27 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"...
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0answers
24 views

CSPRNG unique seeds and proving uniform output [closed]

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
39 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 ...
2
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1answer
50 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 ...
0
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3answers
125 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, ...
0
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1answer
31 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
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1answer
37 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
45 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
votes
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 ...
1
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1answer
35 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 $X$ ...
0
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0answers
12 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 ...
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0answers
30 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 ...
-4
votes
1answer
59 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? ...
0
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1answer
56 views

How modern messengers encryption keys can't be hacked [closed]

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
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1answer
77 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 ...
1
vote
1answer
343 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'':\{...
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0answers
27 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 ...
1
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1answer
30 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 ...
3
votes
1answer
54 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 ...
0
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0answers
25 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
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0answers
16 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?
0
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2answers
61 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
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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0answers
10 views

Finding IV in AES-128 having partial Key and plaintext

Let's suppose we have the plaintext, 14/16 char of the key and the first 2 and the last 36 chars of encrypted data (that is 64 char long). What I want is to find the IV. The cipher algorithm is AES (I ...
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 ...
0
votes
2answers
114 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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2answers
64 views

Why the output of elliptic curve based cryptosystems is smaller than the ordinary public key cryptosystems?

I am trying to understand how much the output of elliptic curve based cryptosystems (for example elliptic curve ElGamal) is smaller than the ordinary public key cryptosystems. I know that the ...
0
votes
1answer
33 views

Learning with rounding (LWR)

This may be a naive question: LWR assumption states that for ${A} \stackrel{$}{\leftarrow} \mathbb{Z}^{m \times n}_q, s \stackrel{$}{\leftarrow} \mathbb{Z}^n_q$, given $(A, \lfloor A\cdot s \rfloor_p$...
0
votes
1answer
38 views

Behavior of AES-CTR with 128-bit nonce and possible overflow

If I feed 128 bits of randomness into AES-CTR as its IV / nonce / initial counter, what will happen if I feed in a random 128-bit integer that overflows and wraps around? I've written a test for this ...
1
vote
4answers
167 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) ...
2
votes
1answer
73 views

Which is the best algorithm for large scale file encryption other than AES?

I've been looking for a fast, powerful and robust algorithm for encrypting large files with authentication . I would like to implement the algorithm on my own without using third party software. I've ...
0
votes
1answer
26 views

Decoding in Reed solomon codes

I have code encoded in GF(7) with primitive 5 Сf(4,1,0,4,5,5). (last four symbols is redundancy) While decoding using DFT we use formula $$ С_k=N^{-1}*c(z^{-kj}) $$ example: $$ C_1 = c(5^{-1*j})/6 ...
1
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0answers
32 views

Very simple way of verification

In an application we need some way for a user to authenticate, but have the challenges of very restricted functions to use. Each user has got a 16bit-number he can't change. We want to calculate some ...
1
vote
1answer
117 views

Entropy Preserving Functions

Let F be a deterministic compression function that takes fixed length 128 bit inputs and outputs 8 bits. Each input to the function has 128 bits of entropy, does that mean that the output byte has 128 ...
1
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0answers
23 views

Block size of BKZ algorithm and related security of CRYSTALS-Kyber

Security of lattice-based schemes in the NIST Posto-Quantum Project often relies on the complexity of dual attack. Complexity of this attack depends on the running time of lattice basis reduction ...
0
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0answers
29 views

Packing technique for large data storage

Packing multiple plaintext messages into a single ciphertext block is known to increase the effeciency of homomorphic encryption. Can someone let me know if this technique can support large data ? For ...
0
votes
1answer
29 views

What does “Clocked” mean in alternating step generators

In the wiki article, it says "An ASG comprises three linear-feedback shift registers, which we will call LFSR0, LFSR1, and LFSR2 for convenience. The output of one of the registers decides which of ...
2
votes
1answer
51 views

If ChaCha20 is being used just as a CSPRNG, is nonce needed?

I'm planning to use ChaCha20 just as a CSPRNG. Key is random (taken from strong initial entropy source) and will be constantly replaced via DJB's fast key-erasure scheme. What should I use as the ...

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