All Questions

-1
votes
1answer
50 views

How does Diffie Hellman protocol work in Bitcoin Blockchain Transactions?

Greetings to all! Please explain how the Diffie-Hellman protocol works in Bitcoin? That is, in Blockchain Transactions, there is also a total number of "K" recipient and sender? "K" the recipient and ...
1
vote
1answer
56 views

What is the minimum message length to obtain the full potential of a hash?

Suppose I want to commit to a uniformly picked nonce of fixed length $n$ bits without revealing the nonce, so I use a secure hash function $H$ mapping messages to digests of length $d$ bits. Suppose $...
0
votes
0answers
9 views

Are compressed pairings used for Barreto-Naehrig curves in practice?

In 2009 Galbraith and Lin wrote the article "Computing Pairings Using x-Coordinates Only" https://link.springer.com/article/10.1007/s10623-008-9233-3, where they proposed to compute pairings on ...
2
votes
0answers
41 views

Derivable encryption key - BIP0032 parallel

I wish to find an asymmetric encryption algorithm that supports key derivation, BIP0032 style. Meaning that I have some SEED [PRIV] and I give someone some public data [PUB], then given new public ...
1
vote
1answer
31 views

Prove in Zero Knowledge the execution of a function

Given a function: $$Y = a * b$$ Is there a way to prove in zero knowledge that a value $Y$ was gotten, without revealing $a$ and $b$? Alternatively, that we have knowledge of $a$ and $b$ such that ...
0
votes
1answer
22 views

Associative Multivariate Permutation

Popular multivariate schemes are constructed by having a several easy-to-invert functions/maps as parivate key, and their composition as the public key. When signing, the hash, or a padded form of ...
0
votes
0answers
22 views

how to call btea() function the original xxtea code [on hold]

I am trying to use XXTEA in an C for a project. The original code in wikipedia shows a function btea() but i don't know how to use it. the original code is as follows: ...
0
votes
0answers
66 views

Cryptography concept concerning keys and key-space [on hold]

What cryptography concept is someone referring to if he says that our galaxy is like key-space and the rest of our universe is like universe of possible numbers where that key-space exists. If you ...
0
votes
1answer
46 views

AEAD using AES-CBC and MAC: how to order the input to the MAC

I'm writing code to provide an AEAD utility. It uses AES-256-CBC for encryption and SHA-512(key+data) truncated to 256 bits as the MAC. ...
1
vote
2answers
72 views

Can a LFSR has more than one repeat cycle?

It's clear that an LFSR has finite states and eventually will end up with repeating cycle. However, is it possible for an LFSR to have more than one repeating cycle? For example, with initial state $A$...
0
votes
0answers
22 views

What books should I read as an introduction to elliptic curves? [closed]

Current Knowledge: Studied Set theory in computer science Basic undergraduate mathematics Basic understanding of Fields and Number theory. Goal: To be able to code Elliptic curves from scratch, ...
0
votes
1answer
37 views

libsodium vs gnupg curve25519 compatibility

I am trying to create deterministic GPG keys based on cryptosteel. I have implemented a library for (de)serializing PGP packets and am now trying to use keys generated in libsodium for import in GPG. ...
2
votes
1answer
45 views

In ECC scalar multiplication, how do `add(Q, Q)` exceptions occur?

Consider some scalar multiplication algorithm for a prime order (Weierstrass) curve $E$ with order $\ell$. Bernstein and Lange's SafeCurves: Completeness page mentions: The problem is that the ...
2
votes
0answers
70 views

Is my deniable encryption scheme reasonable?

I was experimenting with RubberhoseFS, but since it is very hard to compile on anything modern, I decided to implement my own version, stripped of many unnecessary features. Namely, my implementation ...
3
votes
0answers
47 views

Finding maximal $n$-affine subset

We obtained $l$ vectors $B_i$ of $c$ bits $b_{i,j}$. These are an altered form of vectors $A_i$ where the last $n$ bits of each $A_i$ are an affine function of the other bits of that $A_i$. We want ...
4
votes
1answer
101 views

Proving that the least significant bit of an elliptic curve discrete logarithm is $0$

Suppose I have a secret value $a$ which maps to a public point on an elliptic curve $A = a \cdot G$, where $G$ is a generator of the elliptic curve of primer order $q$. Can I prove to someone that ...
3
votes
1answer
73 views

Can this key revocation scheme using hierarchical deterministic keys work?

Assume I am working with crypto that supports hierarchical deterministic key generation, Bitcoin/Ethereum keys using secp256k1 is one example. There is a decentralised key registry where users ...
0
votes
0answers
18 views

How to implement NTRU threshold cryptosystem [closed]

I want to implement a basic NTRU threshold encryption/decryption process, I know the basics of NTRU and I implemented a threshold cryptosystem for ElGamal, the next step is to build one for NTRU, but ...
6
votes
1answer
78 views

How does Twofish avoid weak keys if it uses key-dependent S-boxes?

From section 7.2.2 of the Twofish paper, the four S-boxes for the 128-bit cipher are generated with: $$\begin{align} s_0(x) &= q_1[q_0[q_0[x] \oplus s_{0,0}] \oplus s_{1,0}]\\ s_1(x) &= q_0[...
-1
votes
0answers
19 views

Extract the slave key and encryption key [closed]

I am trying to solve this problem and I need help if possible Suppose a Hardware Security Module (HSM) has a master key KM (56-bit) in its secure memory. It also has a slave key KS (56-bit) ...
-1
votes
1answer
99 views

Creating new cryptographic algorithm instead of using known algorithm

Does it invent a new cryptographic algorithm in case of military encrypted communications makes the communication safer? Keeping the structure and behavior of the protocol unknown is an advantage?
2
votes
1answer
107 views

cryptographic accumulators: accumulator size vs. max. number of set members?

Here's a basic question about cryptographic accumulators, or at least ones based on fixed-size accumulator values (such as RSA ones based on modulo arithmetic), that is strangely not even mentioned in ...
2
votes
1answer
45 views

How to select salt an IKM for HKDF

I have an application where I need to combine a Diffie-Hellman shared secret, with a user's password and derive a key. I'm investigating the possibility of using HKDF to as follows Initial Keying ...
3
votes
1answer
46 views

Question about degree of regularity

I have been reading some papers on cryptography based on multivariate systems and I have a question. How does one relate the difficulty of calculating Gröbner basis (GB) of a multivariate system with ...
5
votes
0answers
42 views

Does there exist trapdoor permutation from lattices?

It seems that the lattice functions are either surjective (SIS) or injective (LWE), due to the error that is basically intended to destroy the structure and provide security. I was wondering whether ...
2
votes
2answers
130 views

What is a good AES mode to use on file encryption?

I'm new to encryption and cryptography, I was wondering if there is a good or best suited AES mode for file encryption (Planning on zipping a folder and encrypt it as a file). If there is, how complex ...
1
vote
2answers
55 views

How many keys in a Hybrid Cryptosystem?

If symmetric cryptosystems have $C^2_n$ keys, and asymmetric systems have $2n$ keys, how many does a hybrid system have? This was in an online quiz from school Company A is considering to adopt ...
1
vote
1answer
49 views

Decrypt simple CBC with XOR

I have searched and my problem is exactly the same as shown here: Decrypt simple CBC message with known IV using XOR encryption However, when I implement the solution it doesn't work, neither does ...
2
votes
2answers
36 views

Why is Blakley secret sharing in finite space?

The paper says it requires a finite space. I wonder what the reason is, since from my understanding it should be perfectly fine to use the "normal" infinite space. So why does Blakley use a finite ...
1
vote
0answers
43 views

Need tips on how to break Fiat-Shamir sigma-protocol (programming challenge)

I'm completely stuck on an university programming challenge and I need some tips to get me out of the valley I'm in, you don't need to give the full answer if you do not wish to. What we have: Fiat ...
16
votes
2answers
4k views

What makes SHA256 secure?

For example, RSA relies on a mathematically hard problem, factoring, while ECDSA or similar rely on discrete logarithm problem. What makes SHA256 and similar hash functions, of the same family, ...
0
votes
0answers
27 views

Develop application using Hyperledger Fabric Java SDK [closed]

I'm modifying an application which uses RSA keys to encrypt and decrypt symmetric keys (which are used to encrypt files). I'm trying to substitute this feature of the central server with the ...
5
votes
2answers
93 views

Is there any hash function that relies on integer exponentiation instead of XOR?

I'm trying to implement a hash function in an esoteric language that has no 32-bit or 64-bit operations. Keccak, for example, is too slow in that language. I'd need a design that minimizes the number ...
2
votes
2answers
60 views

Search Over Encrypted Data

I'm doing a research about how to search over encrypted data as the title said. And, I saw cryptDB used a cryptographic scheme from Song et.al's article Practical Techniques for Searches on Encrypted ...
0
votes
0answers
69 views

Identification of RF hash algorithm [migrated]

I have an unbranded LED lamp with a remote control. I would like to reverse the protocol of the remote but unfortunately I can't create my own packages. The frequency of the remote transceiver is 2....
-1
votes
0answers
31 views

AES-CTR mode using different key's generated trough PBKDF2 in case at least two IVs repeat

Supposed that a client has AES-128 bit randomly generated static key The client is using a PBKDF2 in order to to generate a vector(list) of keys i.e. target keys to leverage will be located ...
2
votes
1answer
27 views

Is it acceptable to add a setup algorithm in the public key encryption?

I saw in the paper How to Use a Short Basis: Trapdoors for Hard Lattices and New Cryptographic Constructions at page 29 that key generation algorithm of PKE can use a common random matrix $A$. Is it ...
0
votes
0answers
22 views

Diffie-Hellman Groups 20 vs 24 [duplicate]

Which encryption under DH has greater Encryption, it's said that the higher the number in DH the greater the encryption but I would like to verify this further. Does Anyone have inputs on this? or ...
2
votes
1answer
59 views

How to make the interactive Schnorr identification protocol become non-interactive

I am reading about ZKP and I found this interesting question about changing this protocol from interactive Schnorr identification protocol to non-interactive and I need help in solving it : Peggy (...
3
votes
1answer
85 views

Generating RSA signature, by manipulating shorter message signatures?

Given a server that can return me RSA sign for any plaintext shorter or equal length of the given plaintext (excluding the given plaintext), how can I fraud/get the sign of the given? $$sign = M^{d} \...
2
votes
1answer
31 views

Using PKCS #11 Certificate Objects for Verification

What is the proper way to use the public key contained in a X.509 certificate with PKCS #11? ...
0
votes
0answers
34 views

How to get unknown constants from linear congruential generator

I need to crack this linear congruential generator. I have $$X_{n+1}=a⋅X_n +b \pmod m$$ I know: $m=31,X_3=30,X_4=19,X_5=26$ How can I find $a,b$ and $X_0$? I have got already the following ...
0
votes
0answers
30 views

How to decrypt a simple substitution cipher where space is also encrypted by a character

I am trying to decrypt a text data encrypted with a simple substitution method with 2 steps. First, shift the alphabet of the source text by a few characters. For example, if we shift by 2 characters,...
6
votes
0answers
85 views

GCM with reversed poly

These slides talk about how GCM can be sped up if one uses $x^{128}+x^{127}+x^{126}+x^{121}+1$ as the reduction polynomial instead of $x^{128}+x^7+x^2+x^1+1$. When one is doing that one needs to ...
3
votes
1answer
108 views

How is Blakley's Secret Sharing Scheme perfect?

Currently, I am trying to understand Blakley's secret sharing scheme. However, there seem to be multiple descriptions of it, which are very different from another, but everyone states that the scheme ...
2
votes
2answers
61 views

Random Self-reducibility in Discrete Log

I understand what Random Self-reducibility means and how it is used in the Discrete Log. What is not clear is how does it show that DL is hard in the average case. The probability of success of an ...
11
votes
1answer
122 views

Why is $e=0$ allowed in Schnorr signatures?

In a Schnorr signature (Wikipedia style), we have: $R = kG$, where $0<k<n$ is a nonce and $G$ is the generator point. $e = H(R \| M) \bmod n$, where $H()$ is a hashing function and $M$ is the ...
0
votes
0answers
38 views

Discrete Logarithm within DH exchange - finding out A and B secret number [duplicate]

How would i find out Alices or Bobs private number from the details exchanged in public. prime - g = 7 primitive root - n = 3 Alice - A = 3 Bob - B = 4 The details visible in public exchange are: ...
2
votes
1answer
41 views

Embedding POW in an EC public key

I have an application where it would be advantageous for an attacker to have to spend a long time generating public keys. To do this, I require that the hash of the public key be less than a certain ...
3
votes
1answer
82 views

What's the Error in This Birthday-Problem Estimation?

Theorem: Choose $Q$ random natural numbers in the set $\{1,2, \dots, M\}.$ The probability of getting at least one collision is $$P_C(Q) = 1 - \frac{M - (Q - 1)}{M} P_{\neg C}(Q-1).$$ Notation: By ...

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