0
votes
0answers
61 views

Is there an “additive” proof-of-work?

I'm trying to find a proof-of-work algorithm with the following properties: If A(1) is a proof of work with Difficulty(A(1))=n (requires n basic operations on average), then one can find a proof of ...
0
votes
1answer
93 views

AES - Encrypting multiple blocks of files

On my site, users can download files which are stored on public hosting, so I need to encrypt them. A downloaded file is divided into blocks of 1 kB and I want encrypt them individually, using the ...
0
votes
1answer
414 views

Java: How to handle authenticated encryption for big files

First I need to mention that I can't use BouncyCastle to implement this solution. I have to encrypt files into the file system. Those files are not going to be tranfered over the wire to any other ...
0
votes
0answers
59 views

Elliptic curve trapdoor function without modular arithmetic?

From what I understand, an elliptic contains a set points satisfying the equation $y^2=x^3 + ax + b$ together with the point at infity. It seems clear how multiplication with a scalar and a point ...
0
votes
0answers
84 views

CP-ABE: structure of the secret key SK

I am working on Ciphertext-Policy Attribute based Encryption (CP-ABE) and I need to understand how a secret key looks like. For example, assume that the universe of attributes is defined to be ...
0
votes
0answers
85 views

proving the security of 1 out of 2 oblivious transfer using AND function

Hello ladies & gentlemen, I need to improve the security of 1-out of 2 oblivious transfer using AND function method with a given info. use one-out-of-two oblivious transfer as building block, ...
0
votes
0answers
85 views

Key generation in Digital Signature Algorithm

In DSA, one needs to generate two primes $p$ and $q$ such that $q$ is $256$-bit and $p$ is $3072$-bit and $p-1$ is a multiple of $q$. Question: How to generate such $p$ and $q$. Attempt: First, use ...
0
votes
0answers
95 views

Importance of ShiftRows in AES

If ShiftRows is excluded from AES, then an attacker can attack the modified AES by simply treating $128$-bit input as $4$ $32$-bits blocks. The attacker can attack these $4$ blocks separately. ...
0
votes
0answers
325 views

Decrypting A Cipher Text without knowing the key or plaintext

i'm new to cryptography and i am doing a research based on cryptanalysis of vigenere cipher. If i have a ciphertext which is encrypted using vigenere cipher, is it possible for me to decrypt the ...
0
votes
0answers
95 views

CCA security of a system that splits messages and encrypts each packet

Propose a symmetric key based crypto-system for implementing a secure email system. This system is based on AES and CCA secure. Suppose that you have to encrypt a large message and that this message ...
0
votes
0answers
111 views

The Inhomogeneous Short Integer Solution (ISIS) problem with a clue

The Inhomogeneous Short Integer Solution (ISIS) problem is as follows: given an integer $q$, a matrix $A \in \mathbb Z^{n\times m}_q$, a vector $b\in \mathbb Z^n_q$, and a real $\beta$, find an ...
0
votes
1answer
211 views

Blowfish ECB mode: Tools for known-plaintext attack?

I'm currently dealing with multiple blowfish-encrypted files that share the same key. All are encrypted using ECB mode judging from their appearance. I don't know what the key is but I know 64 byte ...
0
votes
0answers
26 views

Hokkaido (proof-of-Work system) and pseudo-random permutation table

This question is regarding a proof-of-work system suggested in this article "Cryptology ePrint Archive: Report 2005/356". The outset goal of the Hokkaido algorithm is to provide a task to somebody's ...
0
votes
0answers
53 views

Permutation parity after cycle-walking

Let $E$ be a random even permutation of the set $\{0\dots n-1\}$. We construct a permutation $P$ of the set $\{0\dots m-1\}$, for some $m\le n$, using cycle-walking; that is, computing $P(x)$ is as ...
0
votes
0answers
31 views

openssl - Recommended way to encrypt and sign S/MIME messages using openssl

OpenSSL has two command line tools, cms and smime, that can encrypt and sign S/MIME messages. Both can specify ciphers and ...
0
votes
0answers
50 views

Validity of ElGamal signature variation

I'm trying to solve excersise 7.6 from Hoffstein - Introduction to Mathematical Cryptography page 459 (http://goo.gl/oRyInT) Let $p$ be a prime and let $i$ and $j$ be integers with $gcd(j, p − 1) = ...
0
votes
0answers
47 views

Test framework for hash functions for collision resistance?

I have two questions about the assessment of collision resistance in hash functions. Given a hash-function what would be the next step to inquiry about it's collision resistance / probability of ...
0
votes
0answers
62 views

How can I calculate the size of an encryption key?

I have encryption algorithm that has two variables are used as encryption key. How can I calculate the size of the encryption key. I will show an example of what the variables can be: ...
0
votes
1answer
76 views

Storing salts and iteration number?

I have a function that derives two sub-keys from one passphrase using PBKDF2 one which is used as a encryption key the other for HMAC generation, because these two sub-keys will need to be regenerated ...
0
votes
0answers
103 views

How can I prove CPA secure by using a new scheme gen,enc,dec from GEN,ENC,DEC?

Given public key encryption scheme $(gen; enc; dec)$, we now construct a new scheme $(Gen; Enc; Dec)$ as follows: The key generation algorithm $Gen$ is the same as $gen$. Each ciphertext for a ...
0
votes
0answers
28 views

Do OpenPGP SmartCards have the same or better security than an air-gapped machine?

Are OpenPGP SmartCards, such as the OpenPGP SmartCard V2, suitable enough to have secure communications? Meaning, if I connect my smart card to my Mac which is connected to the internet and always ...
0
votes
0answers
23 views

The number of surviving key after “Meet in the middle stage” in 3-subset MITM attack

In 3-subset Meet in the middle attack, how can we calculate the number of surviving key after meet in the middle stage? and how can we calculate the complexity of Key testing stage? I have read about ...
0
votes
0answers
120 views

recommendation to see documentaries about history of cryptography

Can anybody recommend any good documentaries which go into some history about cryptography and state of cryptography as of date ? I am not asking for favorites or subjective good documentaries but ...
0
votes
0answers
138 views

Franklin-Reiter related message attack m2 = a(m1)+b

As shown in their paper, https://www.cs.unc.edu/~reiter/papers/1996/Eurocrypt.pdf, if one is given an equation relating the two messages m1 and m2 as well as other information one can crack both the ...
0
votes
0answers
97 views

Is it possible to add OpenSSL engine for a block algorithm with different input and output block size?

I need to add a new symmetric cryptography algorithm to OpenSSL, and I thought that the best way to do it is via its engine API. This algorithm will later be used by an application via the OpenSSL ...
0
votes
2answers
183 views

Cryptosystems used to generate public key certificate

Where can we find the cryptosystems used to generate public key certificate? Are the cryptosystems under the signature algorithm and signature hash algorithm? Do I need to analyze the packets ...
0
votes
0answers
53 views

NRPAD and FPAD padding schemes (Korean Seed?)

I've got an API spec that specifies NRPAD and FPAD as possible padding schemes. I see these being used together with the Korean SEED algorithm. The SEED specification however is void of any padding ...
0
votes
0answers
58 views

symmetric encryption A5/1 and A5/2 algorithms

where does the key (Kc) used to generate the keystream comes from and also where does the 22bits counter comes from
0
votes
1answer
103 views

How do I safely anonymize/hash a unique identifier to protect privacy?

I am building a system to collect a unique identifier (MAC addresses from 802.11 probe requests). The system will have several collection points over a large area, submitting to a central database. I ...
0
votes
0answers
25 views

Fast root finding algorithm for Binary Goppa codes decoding using linearised and affine polynomials

I am trying to implement the root finding algorithm from the following paper - Finding roots of polynomials over finite fields by Sergei V. Fedorenko, Peter V. Trifonov link : ...
0
votes
0answers
83 views

Is a RSA 2048 bits public key secure [duplicate]

I realize servers such as Google, Yahoo, which use RSA has 2048 bits public key. After comparing those keys, I realize that the public keys share a common property, that is first 9 bytes and last 5 ...
0
votes
0answers
158 views

The Short Integer Solution (SIS) problem for square matrices

The short (or small) integer solution (SIS) problem is as follows: given an integer $q$, a matrix $A \in \mathbb Z^{n\times m}_q$, and a real $\beta$, find a nonzero integer vector $e\in \mathbb Z^m$ ...
0
votes
0answers
29 views

A5/1 and LFSR incrementation

I am working on A5/1 and I'm not sure to all understand about it. We consider that we receive a burst(228 bits-sequence) to encrypt every 4.615 milliseconds. So when we have initialized our LFSR's ...
0
votes
0answers
27 views

signed message susceptible to block re-ordering , block deletion , block replication

We would implement a Public Key Cryptography (PKC) based digital signature by breaking the message into blocks and signing each block independently. One of the issues associated with digital ...
0
votes
0answers
59 views

Low exponent attack against RSA

According to this: http://www.cims.nyu.edu/~regev/teaching/lattices_fall_2004/ln/rsa.pdf One can calculate the message m, if there was no padding scheme involved. My question: is it possible to find ...
0
votes
1answer
85 views

Symmetric vs non-symmetric pairing based crypto

I am trying to find a comparison of how different pairing-friendly elliptic curves perform (in terms of security) in real world applications; I am using PBC library, and it has type A curves and type ...
0
votes
0answers
26 views

Help in uderstanding NIZKPoK notation (and how to code it) needed

Hello fellow cryptographers I have a rather silly question for you; I am aware of how Schnorrs NIZKPoK / SoK works when someone must prove knowledge about DL: y = g^x; (and how to code it) RFC ...
0
votes
0answers
148 views

Serpent 256bit Non bit sliced version (Table Sbox/IP/FP/LT/ILT) (Non-bitslice notation rules)

Good afternoon! I got some mismatches while counting Round Keys at non bitsliced version of Serpent. I have used official AES submission outputs (file ecb_iv.txt). AES submission package test vector: ...
0
votes
0answers
75 views

Public key encryption without ciphertext expansion

Say I have a database column that is defined as VARCHAR(255) that stores names. I can assume that names can be up to 255 chars. I need a public key encryption so that I can replace names with their ...
0
votes
0answers
49 views

Password generation/storage scheme

How bad is the following strategy for a password manager on a local machine? The user wants to sign up for somesite.com where he needs a password. The user has previously generated a secret key ...
0
votes
0answers
30 views

Elliptic Curves Readdition

I found the term re-addition in https://www.hyperelliptic.org/EFD/g1p/auto-shortw-projective.html and I cannot figure out what it is. It has actually same complexity of addition and I dont see the ...
0
votes
1answer
96 views

A one way Function provably reversible at N applications with the same seed?

I'm looking for a function that is generally one way from some secret $F(s, A) \rightarrow Y$, where $A$ is known, $Y$ is produced (also known), and $s$ is kept secret. But whose repeated application ...
0
votes
0answers
25 views

Computing the redundancy of language for a Vigenère cipher with m=5

Redundancy of L = 1- Entropy of L/ log base 2 {P} The Redundancy of L is given by 1 minus the Entropy of L divided by log base 2 of the Cardinality of the Plaintext space. Could someone advise me how ...
0
votes
0answers
73 views

initiate the elliptic curve

when we consider a curve in a prime field for example Weierstrass form and want to initiate it in Miracl,we should give these inputs for initiate curve: ebrick_init(&binst,x,y,a,b,n,window,nb) ...
0
votes
0answers
186 views

Existential Unforgeability of signature scheme against Adaptive Chosen Message Attack

While reading a literature on signature schemes, I came across the concept of Existential Unforgeability of signature scheme against Adaptive Chosen Message Attack. Can anyone point me to the paper ...
0
votes
1answer
100 views

I need to know number of encryption/decryption operations? [closed]

If i want to break quadruple DES (say EDED), what is complexity? Like for EDE, it is O(2^112).
0
votes
0answers
54 views

Forward Secrecy with pseudorandom functions

Let $H_1$, $H_2$ be keyed hash functions (e.g. $H_i(x) = SHA_{256}(s_i||x)$ for pseudorandom $s_1$, $s_2$). Let $s_n = H_1^k(s_0)$, $k_n = H_2(s_n)$, where $s_0$ is a secret (pseudorandomly chosen ...
0
votes
0answers
90 views

Generating a public key certificate with ECDSA params

I have an ECDSA key generated in a HSM and I am able to retrieve it's public key components via the PKCS11 library. I would like to create a public x509 certificate with the public params for the ...
0
votes
0answers
79 views

Bit level permutation

Could anyone explain how secure is bit level permutation? What is the most serious threat against the security of this kind of cipher? Thank you
0
votes
0answers
171 views

how to find key matrix in hill cipher

I want to solve this problem but there are 3 known plaintext-ciphertext pairs. The key of Hill cipher is a 3*3 matrix as k=[k1,k2,3; k4,k5,k6; k7,k8,k9] where the unknown ...

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