1
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1answer
214 views

ECDSA - point order criterion

i am creating some primitive demostration for ECDSA over small curve (p < 229). But my implementation have some weird issues. Verify process return false even if the signature is correct. Because I ...
1
vote
1answer
118 views

Determine complexity of a SAT problem

Is there a standard way to determine a complexity of the specified SAT problem? I'm researching algebraic cryptanalysis and came to solving multivariate quadratic equation systems using CryptoMiniSat. ...
1
vote
1answer
165 views

Is it possible take a piece of data in secret?

I want something like this, but in a digital sense: You and others walk into a room. Everyone knows who each of you are and everyone is doing their best to figure out what piece of paper each ...
1
vote
1answer
352 views

Which encodings have |encoding key| >> |decoding key|?

I'm looking for an encoding scheme that requires a very large encoding key E (>10MB) and suffices with a relatively small decoding key ...
1
vote
1answer
216 views

Block ordering and security in a MAC?

To authenticate a message $m = m_1 \,\|\, \dots \,\|\,m_n$ the tag $t := F_k(r) \oplus F_k(m_1) \oplus \dotsb \oplus F_k(m_n)$ is used, where r is uniform random number $(0,1)^n$ and $m=(0,1)^n$. Even ...
1
vote
1answer
280 views

Is the SILC protocol still used? [closed]

I'm looking into implementing a private SILC server for friends (and possibly their friends). And after visiting the Wikipedia entry for SILC protocol, it seems all the official pages linked at the ...
1
vote
0answers
17 views

Is Shamir's Secret Sharing Scheme insecure for larger field?

According to wikipedia, if you are using shamir's secret sharing scheme with a field of order $p$, "High values of $p$ are risky because Eve knows that the chance for $f(x)\pmod{p}=f(x)$ increases ...
1
vote
1answer
18 views

Create big random number from 2 smaller numbers?

If I have 2 true random numbers from atmospheric noise or a different source. Suppose $x= 299$ and $y= 499$. Is it possible to create a bigger number with $x$ to the power of $y$? Can I use ...
1
vote
1answer
62 views

Diffie-Hellman key size to symmetric formula?

I've noticed that on every site I checked I kept finding the relationship between D-H key size and symmetric encryption equivalent as a table, like: 384 - 56 768 - 80 1792 - 112 2304 - 128 10753 ...
1
vote
1answer
28 views

How to construct Hash function of type H:{0,1} * X G -> Zp*?

In many cryptographic protocols design, I have seen the statement 'Choose a Hash function H1:{0,1}* X G -> Zp*' i.e a hash function which takes as input a binary string of finite length and a random ...
1
vote
1answer
25 views

Is it safer to use timestamp in REST authentication?

I am working on a personal project to build a REST authentication system which authenticate clients via three parameters: ...
1
vote
3answers
34 views

Possible to generate a one time secret which all nodes on the distributed network can know but cannot pre compute

I have a distributed P2P network. Everyday, I want each node to have a secret which is only valid for that day, while each of the other remaining nodes on the network will be able to calculate the ...
1
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0answers
37 views

Caculated time One Point Multiplication with double and method

I am using double and add method for point multiplication in affine coordinates. How we compute 1PM in double and method? Di Wang said one point multiplication consists of repeated addition and ...
1
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0answers
13 views

Attribute based access control and role based, online bookstore example

I am asked to answer a question that says: One online book-store wants to grand access to clients regarding their subscription. There are 3 types of subscriptions A , B and C. Customers get access ...
1
vote
1answer
48 views

Ciphertext with uneven letter distribution

I have a ciphertext encrypted with an unknown method. It is part of a challenge (personal quest), so I can not post it. The letter statistics is the following: ...
1
vote
0answers
18 views

How big window is secure and practical with TOTP? [migrated]

We are using Time-based One-time Password Algorithm (Google Authenticator) in our system. Since we currently don't allow any time window and code validity is just 30 seconds, we are constantly having ...
1
vote
2answers
39 views

Linear cryptanalysis complete key guessing

In linear crypt analysis, partial sub keys are guessed and verified for its correctness with the help of plaintext and ciphertext. From the partial sub key, how it is possible to guess the complete ...
1
vote
1answer
78 views

Why does a fixed key not make MACs like CBC-MAC or GMAC into secure hash functions? [duplicate]

Why does setting the secret key to a fixed, public value not make MACs like CBC-MAC or EMAC into secure unkeyed cryptographic hash functions? In other words, why is the resulting hash function not ...
1
vote
0answers
24 views

Breaking Vigenere via Kasiski/Babbage method? (non-programmatic)

I'm really hoping someone can explain to me what is going on in the second major component of this form of analysis. If you wish, for convenience, here's a page that already has some ciphered text ...
1
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1answer
39 views

RSA PKCS#1, v1.5 padding output

If I make use of RSA PKCS#1 in v1.5 what padding length is used. Basically, it is not allowed that the plaintext is bigger than the modulus. But what if the length in bits is the same (padding to ...
1
vote
1answer
48 views

Is multiplicative blinding less secure than additive?

It's easy to see that additive blinding (e.g., $x+r$ for secret x and random r) is perfectly secure in a finite field (this is a one-time-pad) and statistically secure for $r$ uniformly distributed in ...
1
vote
1answer
85 views

How to find roots of equation $f(x)=0 \pmod p $, where $p$ is prime number?

$f(x)$is any nth degree equation $n>0$, how to find roots of $f(x)$ over prime modulo.
1
vote
1answer
29 views

Cardholder to Merchant SET Protocol

I have some doubts regarding the SET protocol. Let say the Alice payment information runs through a sha-1 hash function which is a one-way algorithm, irreversible to create a message digest. How do ...
1
vote
2answers
56 views

ECDH-ECDSA Combination

I am doing research on cryptography primitives at a basic level and I faced a question on encryption methods. I understood that ECDH is an approach to for secure key exchange between two parties ...
1
vote
1answer
44 views

construction of division polynomials

I'm not sure if this is the right place for my question.... I'm trying to understand the construction of the division polynomials used in the schoof algorithm. I firstly followed the report of ...
1
vote
0answers
21 views

Faster discrete Gaussian sampling

Our goal is find a faster discrete Gaussian sampling to solve $"SVP"$ problem in lattice: A lattice is discrete subgroup of $R^n$ such that define as below: let $\{b_1,\cdots ,b_n\}$ be a basis in ...
1
vote
0answers
47 views

Data integrity using steganographic methods

I am looking for a lightweight and fast (almost real time) data integrity checker for a very time critical application. Is it possible to provide data integrity using a steganographic method, lets say ...
1
vote
1answer
22 views

ABE Schemes - Access Structures & Performance

I'm reading this article, CP-ABE with constant-size keys for lightweight devices and in the Table 1, are there these access structure: Threshold, Tree, ($n$,$n$)-Threshold, LSSS, AND gates. I have 2 ...
1
vote
1answer
20 views

Key Exchange MAC encryption order of events? Problem

I want to write the sequence of events of how a MAC encryption works for documentation at work. For this purpose I have a document (given by my boss to me) in German and I am trying to translate it ...
1
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0answers
63 views

When we use one time pad TWICE in two different ways

Assumption and Notations: All the values defined over the field $\mathbb{F}_p$, where $p$ is a large prime number. We denote multiplicative inverse of value $v$ by $v^{-1}$. All values are non-zero ...
1
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0answers
29 views

Need help with PKCS#12 3 key triple des key expansion

I am trying to decrypt PKCS8-Shrouded Key Bag inside a PKCS#12 pfx file. The oid for the encrypted data is PbeWithSHAAnd3-KeyTripleDES CBC. Iteration count and salt has been provided within the pfx ...
1
vote
0answers
41 views

Vulnerabilities in SHA-1 [duplicate]

Are there any known vulnerabilities in SHA-1 that can be exploited? Certain patterns that it shows? I recently performed a frequency analysis using 20,000 common words, and found nothing exploitable. ...
1
vote
0answers
40 views

Compressing AES [duplicate]

I have this program which encrypts multiple files using AES then compress it using LZO into one single file. The problem is that the final file is almost equal in size than all the files which means ...
1
vote
0answers
19 views

Security issues with self encryption? [duplicate]

I'm thinking about the scenario of using a set of (potentially untrusted) hosts to store (potentially private) files. Think something like distributed backup where you contribute some disk space and ...
1
vote
0answers
13 views

Do Wegman-Carter authenticators allow key reuse if the authenticator result is kept secret?

Poly1305 (and GHASH) are secure authenticators, but only for one use. Thus, nonce reuse in Poly1305-AES, ChaCha20-Poly1305, and AES-GCM all reveal the authentication key. However, my understanding ...
1
vote
0answers
17 views

Are there known practical attacks on RC4-dropN? [duplicate]

RC4 is known to leak information about the first few bytes of the ciphertext due to keystream biases. However, are there known attacks on RC4-drop[N] where N is large enough, that leak information ...
1
vote
1answer
21 views

Do any Identity-based Encryption Systems support messaging between domains?

Identity Based Encryption is covered under RFC 5091 (specifying the algorithm), 5408 (specifying data structures), and 5409 (using IBE with Cryptographic Message Syntax). However, every IBE ...
1
vote
1answer
22 views

Role of Fermat's little theorem in the proof of correctness of ElGamal signature

In the Wikipedia article about the ElGamal signature scheme it is written, that Fermat's little theorem is used in the following proof of correctness: From the signature generation in ElGamal we can ...
1
vote
1answer
82 views

Using e-ID Number for Encryption and Digital Signing

I want to use e-ID number for performing Encryption/Decryption and Digital Signing - and in order to do so, I've opted a PGP-oriented approach which goes a bit like this. Generating PGP key-pair ...
1
vote
0answers
19 views

If you use an AES key just once, do you need to use IV, and/or pad the message? [duplicate]

I am developing an application that is going to use AES encryption. Since it is going to use a different key for every message encrypted... Would it be secure to use a constant IV? (i.e null bytes) ...
1
vote
0answers
33 views

Convert projective to affine coordinates in ECC? [closed]

I am working with my project. I use projective coordinates but when I convert to affine coordinates, I can't get it. Can anyone help me? Projective Coordinates $(X,Y,Z)$ to Affine Coordinates ...
1
vote
0answers
47 views

Diffie-Hellman, RSA and the types of public key cryptography

Are these schemes fundamentally different? Are other schemes fundamentally different in the sense that you can do different operations with them (or the same operations, but needing different ...
1
vote
0answers
37 views

Algebraic relationship between Original Key and Sub Key of DES

Does there exist any sorts of algebraic relationship between Original and Sub Key of DES? I understand that by solving K-Maps of 64-bit Input/48-bit Output, I can get 16 algebraic relationships ...
1
vote
0answers
52 views

Encryption technology for DARPA

I'm working on a short story taking place in the near future in which a hacker gains access to the DARPA mainframe and files related to a highly classified DARPA project. Being ignorant about state ...
1
vote
0answers
87 views

Example of FHEI scheme?

I am reading this paper Toward Secure Multikeyword Top-k Retrieval over Encrypted Cloud Data. I am trying to work out an example of the FHEI (Fully homomorphic Encryption over Integers) scheme ...
1
vote
0answers
14 views

References for cascade [closed]

I have found many sources against cascading encryption, however I am having trouble finding arguments FOR using cascading. AES-256 + BlowFish + RC5 etc... each with a different key. This is for ...
1
vote
2answers
78 views

Homomorphic encryption diagram and trouble about a paper

I'm reading a paper based on Homomorphic Encryption: “Fully Homomorphic Encryption over the Integers: From Theory to Practice” (PDF). Now, I need a diagram of this algorithm if possible with all the ...
1
vote
0answers
37 views

PBC library: group of composite order for pairing operation

How to generate composite order group using PBC library? With PBC library, element_init_G1(g,pairing) statement creates element $g$ for group of prime order. I want ...
1
vote
0answers
59 views

Encryption used in a commercial software product [closed]

I found (through some reverse-engineering) that the following encryption scheme is used in a commercial software that is quite widely used in Germany (Security by obscurity at its best). I have the ...
1
vote
0answers
57 views

What can I do to improve my encyption method [closed]

I'm new to cryptography and I want to learn more. For me, the best way to learn about something that I have no experience with is to experiment and I've coded a very basic approach to a simple ...

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