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Methods and tools for Plain-text Attacks

I have a data block of about 950 byte (previously encoded in QR code). The data is encrypted with an unknown algo+key. The bright side is: I already know many parts of the message, and I have multiple ...
6
votes
1answer
592 views

Small error in security proof on the paper On the Multi-User Security of Short Schnorr Signatures with Preprocessing

I think I found a small error in the security proof Link end of page 37. It states that $ \sum_{i\leq q} \frac{3i+2}{p-(3q +2)^2/4} \leq \frac{3(q +1)q/2+2}{p - (3q +2)^2 /4}$. But shouldn't it be $\...
0
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0answers
16 views

Cryptography + Programming + Mathematics [migrated]

I am PhD student of Mathematics already done with my thesis. My research field is not related with cryptography but I have been keeping good interest in number theory and algebra which I assume to be ...
3
votes
2answers
253 views

Time Complexity Of Solving DLog When g and P are known

This (https://en.m.wikipedia.org/wiki/Discrete_logarithm) Wikipedia article confuses me. If you have the equation a = g^n (mod P), and g, P and a are all known, then how does a brute force solving for ...
2
votes
0answers
30 views

How to convert plaintext to element of cyclic group in Cramer-Shoup cryptosystem

I am trying to implement a cramer-shoup cryptosystem but I don't understand how to work with the plaintext I want to encrypt. From what I understand, the plaintext needs to be converted to an element ...
0
votes
1answer
24 views

Issues generating keys/cyclic group for Cramer-Shoup Cryptosystem with OpenSSL

I'm trying to implement a Cramer Shoup cryptography system in C but I've run into problems with generating the keys. From what I have found on the wiki and in other papers, to generate keys for Cramer ...
0
votes
2answers
41 views

Can two parties with a common secret jointy issue a commitment?

Let's say parties A and B have a common secret $k$. Is there a protocol where both the parties jointly release a commitment to $k$ so that later on, neither A or B can deny what the common secret was? ...
4
votes
1answer
92 views

Unable to understand notation regarding Shannon's theorem

the following equation is used to prove the Shannon's theorem by showing the existence of two messages $m_0, m_1$ if $|K| < |M|$ but I'm unable to visualize/understand the probabilities. Especially ...
27
votes
4answers
4k views

Why is FIPS 140-2 compliance controversial?

I was reading the comments of an article about a proposed new implementation of /dev/random in Linux today, and someone remarked that it must be bothersome to go ...
-2
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0answers
24 views

How can I check total number of unique wallets buying a specific smart contract [closed]

I am not a developer, I am just trying to understand transactions. I want to know how many wallets or accounts are trying to buy a particular token. For example: MILK2, how may unique wallets/accounts ...
4
votes
1answer
93 views

ZKP: Prove that >18 while hiding age

I am relatively new to cryptography, but I've been programming for a while. Here's a story that sets well the problem I'm trying to solve: Alice has a digital passport that's signed with her ...
0
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1answer
54 views

What Is The Maximum Value For N In Discrete Logarithm Problems?

I have some code, which can crack a discrete logarithm problem in ~ O(0.5n) time. However, this only works if, in the following, N is less than P: G^N (mod P). To be clear, my program can figure out ...
1
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0answers
25 views

The relationship between root hermite factor and bit-security?

The root hermite factor corresponding to an bit-security level, such as 1.0045 corresponding to 128-bit security. What is the root hermite factor corresponding to 100-bit, 160-bit, 180-bit security? ...
1
vote
1answer
71 views

how high is the possibility of getting a hash collision in text files?

Just for an example, let's say I downloaded "the adventures of tom sawyer" from gutenberg in .txt file format and saved it to my usb thumb drive. And as you can see, usb drive is not an ...
3
votes
2answers
190 views

Are PRNGs Key Derivation Functions?

PRNG is a mechanism to produce randomness from an initial random seed, so basically a way to derive more secrets from one secret. Looking at the Wikipedia entry for KDF you find In cryptography, a ...
0
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0answers
30 views

How is this step being calculated and why is that getting the factors is able to determine private key or universal forgery?

https://link.springer.com/content/pdf/10.1007/3-540-49649-1_18.pdf In class I, why (4) implies $g\equiv 1 \mod q$ Also even though I get $p$ and $q$ it still can't get $ord_n(g)$ without trying out ...
0
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0answers
31 views

Modes of operation for public key encryption [duplicate]

Why do we not define modes of operation for public-key encryption just like how they are defined for block ciphers?
1
vote
2answers
127 views

Is it safe to store the hash of a plain text?

When encrypting data, I want to verify that the correct key was entered without hashing it. Is it safe to decrypt the ciphertext and compare the hash of it with the stored one or can the plaintext (...
0
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0answers
29 views

PRG implies OWF Proof

I got the idea of this proof, that since PRG expands from n to 2n, it cannot project to all {0,1}^{2n}, only to a neglible part which we can abuse to make a good distinguisher just by telling if A ...
1
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0answers
35 views

Secure protocols with the dynamic programming solution concept?

Suppose that we have the usual problem of secure communication, where each of the $I$ agents have a private signal $s_1,s_2,\dots,I$ and they wish to compute any function $f(s_1,s_1,...,s_I)=(x_1,x_2,....
0
votes
1answer
39 views

How to find iteration exponent in a cycling attack?

In Simmons and Norris paper they demonstrate the cycling attack with the following example: p = 383 q = 563 s = 49 and t = 56957 ( a prime) The attacker knows the publicly available r = pq = 215,629 ,...
3
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0answers
56 views

What are Practical Primitives based on Lattices, LWE and FHE?

Lattice-based cryptography is being used for several primitives and applications. I know there are newer works for PIR, PSI, ORAM that have seen tremendous improvements due to FHE. In some cases, FHE ...
1
vote
0answers
30 views

THe operation proof part of paper "Why and How zhSNARK works"

I'm reading the paper "Why and How zk-SNARK works" to learn zkSNARK, and I suffered some problem in section 4.4, when prove the ability of single operation. In this section, it tries to come ...
0
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0answers
22 views

How to estimate the parameter of a lattice signature scheme with lossy reduction?

The parameter of a lattice signature scheme DAZ19 with tight reduction can be choosed to make the underlying hardness problem intractable. How to estimate the parameter of a lattice signature scheme ...
1
vote
4answers
101 views

Does SSL connection provide integrity?

I'm new to cryptography and I'm trying to implement a secure chat application using OpenSSL. I want to ensure that public messages (which will be shown to all users) cannot be altered during ...
1
vote
0answers
22 views

Key Switching Error in CKKS

I believe I am misunderstanding something about the bounds derived for the key switching error in CKKS. I will refer to the initial paper, but similar bounds have been derived in all variants I have ...
0
votes
0answers
38 views

Does the number of bits in the block nonce influence the security of the blockchain?

I know that Bitcoin uses a 32bit nonce that miners iterate over trying to hit the target number of prefixed 0's in the hash. If they run through all 2^32 combinations they then change something else ...
-3
votes
0answers
39 views

How do you quickly find D? (RSA) [duplicate]

with small primes under 1000 each i can find D in a matter of less than 1 second but anything above 1000 seems like it could go on forever! right now I generated huge primes (p = 9504941263, q = ...
2
votes
1answer
96 views

How strong if I combine two hash functions, such as MD5(SHA256(input))?

If I try to do MD5(SHA256(input)), what is the strength of this so-called double hashing approach? Is it as strong as SHA256, or as strong as MD5, or as strong as ...
3
votes
0answers
36 views

parameter estimating in lattice signature scheme

when reading [BDLOP18], I run the lwe-estimator with the recommended parameters in Table 2 , but the result of hermite factor is 1.007, this result is bigger than the recommended hermite factor 1.0035
1
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0answers
35 views

Approval of GPG key strategy [migrated]

I am a beginner in anything related to GPG and I have now read quite some stuff about it to get a better idea. I think i grasped most of the concepts by now. I've worked out a GPG key strategy and i ...
1
vote
2answers
90 views

In AES-256, what exactly forms the extension field $GF(2^8)$?

My question is a little difficult to describe, so let me first start with an analogy In an elliptic curve over a finite field, there are 2 groups - the first group is a finite field over which the ...
2
votes
2answers
67 views

*-LWE equivalent of Diffie-Hellman $g^{x^2}$ vulnerability

In Is Diffie-Hellman less secure when A and B select the same random number? , the possibility of Diffie-Hellman key exchange producing identical peer keys and the vulnerability of it against passive ...
1
vote
1answer
64 views

How to check security strength of random k if k is an input parameter of ECDSA signature generation function using openssl-fips

As I understand, 1.The security strength is specified in bits according to https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-90Ar1.pdf 2.Security strength is depend on the length of ...
3
votes
1answer
78 views

What hash based digital signature algorithms exist that have reasonably small signature sizes?

What hash based digital signature algorithms exist that have reasonably small signature sizes? By reasonably small, I mean not much bigger than what you would get with a 256-bit ECDSA (which I ...
1
vote
1answer
61 views

Is asymmetric decryption guessable?

I am not an amateur in cryptography so this might be a very basic question. I am interested to know if there exist ciphers such that if I encrypt a message with it and then lose first say 300 bits ...
2
votes
2answers
115 views

Why do people use protocols like PGP, when TLS already exists?

TLS is the standard cryptography protocol on the internet, and many websites use it to secure their communications. However, for personal use, most people use other protocols like PGP, instead of ...
0
votes
0answers
37 views

What happens when we hash already hashed values, concatenated together?

I read on the page 16 of On the Security of Hash Function Combiners that the classical combiner for collision-resistance simply concatenates the outputs of both hash functions $Comb_{\mathbin\|}(M) = ...
0
votes
1answer
71 views

Signing same message 2 times with ECDSA

Can multiple signatures of the same message with the same private key (different nonces) lead to a private key trace?
0
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0answers
6 views

Can a 'China' or similar actor with more than half of the hash power really destroy Bitcoin? [migrated]

More of a general question as I've recently gotten into investing in cryptocurrencies. I really love the vision for the future this technology provides, the freedom, ease of use, lack of middlemen, ...
1
vote
0answers
40 views

Birational transformation from Edwards curve with not square d to Edwards curve with square d

How can I transform a complete twisted Edwards curve $ax^2+y^2 = 1+dx^2y^2$ with not square $d$ and square $a$ into an isomorphic Edwards curve $X^2+Y^2 = 1+DX^2Y^2$ with a square $-D$ i.e. $D = -r^2$?...
2
votes
1answer
60 views

Sage code for finding generator matrix of MDS code

Let $L$ be an $[n,k]$ code. A $k\times n$ matrix $G$ whose rows form a basis for $L$ is called a generator matrix for $L$. A linear $[n,k,d]$ code with largest possible minimum distance is called ...
0
votes
0answers
30 views

Security of verifiable shamir secret share

Let us consider the following verification protocol based on Feldman. Assume, $c_0,\cdots,c_k$ represent the coefficients of the polynomial $p()$ in $\mathbb{Z}_q$. For verifying share $(i,p(i))$ and ...
1
vote
1answer
89 views

Unhash possible? How got this user the unhash?

in this post Why can't we reverse hashes? there is an unhash of "Hello World". How did that work? If there is no function to find it, where does it come from?
4
votes
1answer
141 views

What are the misconceptions of IBM's CEO Arvind Krishna talk on the "Axios on HBO" about the quantum computing

IBM CEO Arvind made a talk in HBO's Axios program. It seems that there are misconceptions/misleading/flaws in reasoning etc. What are those! Some of the details of the speech is given as; IBM says ...
2
votes
1answer
75 views

What is reaction attack?

In the paper of "Reaction Attacks against Several Public-Key Cryptosystems" CiteSeerX link, reaction attack is defined informally as "Obtaining information about the private key or ...
1
vote
1answer
34 views

How are cryptographic tokens and secret keys different?

Can someone throw light on the differences between tokens and secret keys? I understand that "tokens" are crypto artefacts "introduced" into a system by an external party in order ...
0
votes
0answers
22 views

Securely and Deterministically select a combination of objects from hash (cryptographic seed)

I am working on a project that is using a bit-commitment concept to authenticate information. I need to select a combination of objects securely from a secure hash, then distribute that hash later. ...
0
votes
0answers
35 views

Is it possible (and if so how) to make one proof for multiple private keys in ECDSA

Lets say I have a message that needs to be signed by two keys that were generated using ECDSA Is it possible to make a signature that accounts for both keys, meaning I can verify with both and see ...
2
votes
1answer
334 views

Linear Complexity of two dimensional finite patterns such as QR codes

Two dimensional patters are omnipresent in information transactions. QR codes, images are most common. I want to know if there is a concept analogous to the well known concept of Linear Complexity of ...

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