0
votes
2answers
63 views

Using the Vigenere Cipher to find key

Given a ciphertext message that was generated using the XOR cipher and a bit string found in the plaintext, how can you find the key that can be used to map the plaintext to the ciphertext?
-3
votes
0answers
47 views

AES or Serpent-Twofish-AES [closed]

I want to encrypt my private stuff like credit cards, money, RSA private keys (and so on) but I don't know if I should use AES-256 only or in combo like Serpent-Twofish-AES (I am using Veracrypt). ...
0
votes
1answer
51 views

Encode-decode with different block sizes? [closed]

I am implementing AES-ctr encryption. While encrypting I call dofinal on every 16 bytes of data. When I try to decrypt this data in different chunk size say 32 bytes I get different output (original ...
2
votes
1answer
58 views

Comparing n-multiple amount of merkle trees?

I would like to know what best steps are there in finding differences between a high order amount of merkle tree's or if a better associative structure should be used. I ask this questions because ...
0
votes
0answers
53 views

Collision attacks on digital signatures

After reading this document about MD5 collision attacks, I still don't understand how collisions can make digital signatures insecure. In the paper, the researchers created two files with the same ...
-1
votes
0answers
31 views

Can anyone explain how IV(Initial vector ) are chosen in GCM and in CBC MAC in detail?

I actually want to know in detail regarding the IV selection in CBC MAC and in GCM MAC. There is difference in IV between CBC encryption and CBC MAC. Please explain about MAC.
0
votes
0answers
39 views

RSA: If I know n, e, p, and q, how do I calculate d using the extended euclidean algorithm? [duplicate]

After doing a good amount of research, it's become fairly obvious that I ought to be using the extended Euclidean algorithm to calculate d from the data that I already have. However, this isn't an ...
0
votes
0answers
43 views

common ways / methods to try to break a SP network

I have a very little cryptography background (but a relatively solid maths background) so my below question is very general. Basically I have been given a SP network with an output to reverse. I ...
4
votes
1answer
121 views

Can machine learning analyze random number generator?

I'm studying for random number generators(RNG) and I saw about machine learning a few days ago. So I searched analysis of RNG using machine learning. But I couldn't find such fields. Are there such ...
2
votes
4answers
155 views

Computation indistinguishability questions

The definition I have is: Two probability ensembles $X = \{X_n\}_{n \in \mathbf{N}}$ and $X = \{Y_n\}_{n \in \mathbf{N}}$ are computationally indistinguishable if for every probabilistic ...
2
votes
1answer
43 views

Is it secure to transmit a short plaintext with its MAC?

I have a short (32-bit) message that needs to be authenticated. Due to the constraints of my platform, I would like to use Speck32/64 (32-bit block, 64-bit key) with a Matyas-Meyer-Oseas one-way ...
1
vote
1answer
63 views

NTRU Encryption

It's using Euclidian inverse. Can you show it step by step? $$N=7, q=11, a = 3+2X^2 -3X^4 +X^6$$ the inverse of $a \pmod {11}$ is $$A=-2+4X+2X^2 +4X^3 -4X^4 +2X^5 -2X^6$$ How do we compute $A$?
1
vote
3answers
72 views

Does perfect secrecy imply uniform ciphertext distribution?

I suspect the answer is no, but I am not able to either prove it, or provide an example. In Katz and Lindell's book, it is only said that with a perfectly secret encryption scheme, the plain and ...
2
votes
1answer
30 views

Discrete log accumulator without pairings

Here $g$ is some fixed generator of a discrete log group. I don't want the group to be bilinear for efficiency and BDH-skepticism reasons. Is anyone aware of a discrete log accumulator? What I mean ...
0
votes
1answer
47 views

Blum primes [x=3(mod 4)] zero knowledge proof?

Lets say we have 2 primes, $p \equiv q \equiv 3 \pmod{4}$, and we make $n=p \times q$ public. I can, without revealing factors, show that $n$ has two prime factors. How can i zero knowledge prove ...
1
vote
3answers
88 views

Cycles in SHA256

In the recommendations, it seems cycles is used usually as in "CPU Cycles", but, that's not what I mean here. What I mean, is this: Let's say I start with a particular 256 bit value. Call this v. I ...
0
votes
0answers
8 views

How to import key BLOB generated from Microsoft CryptExportKey from Linux [migrated]

I have a private/public key pair saved as key BLOBs which were in fact exported with the Microsoft "CryptExportKey" API. Now I need to use the same key pair (specially the public key) under Linux ...
0
votes
1answer
83 views

Are modes of operation algorithms practical?

I took a cryptography class back in college, and now that I am working my 1st career one of the things currently on my plate is coming up with an algorithm to encrypt data before it's placed on the ...
1
vote
2answers
73 views

Hash function such that fx(hash(s1),hash(s2)) = hash(concat(s1,s2))

First, I'm not a mathematician, so I may express this question awkwardly. Feel free to chuckle. I'm wondering if there exists a hash function h such that for given strings s1 and s2, and string ...
0
votes
1answer
64 views

RSA weak padding

Suppose to have a function for numbers expressed in 8-bit $\in [0,2^8-1]$ defined as: $$f(x)=x||x||x||x$$ where $|f(x)|$ is exactly 32 bits. e.g., suppose x=2 (00000010) so ...
1
vote
1answer
49 views

Authentication using a one-time pad

I am building a small embedded system of two nodes that communicate wirelessly. The microcontrollers I'm using are very limited: they only have 256 bytes of RAM. I would like to be able to ...
2
votes
1answer
148 views

What is this cryptosystem called?

From a paper Outsourcing Large Matrix Inversion Computation to A Public Cloud (IEEE Transactions on Cloud Computing, Vol. 1, N°1, 2013; alternate source requiring registration; preprint), I got to ...
0
votes
1answer
35 views

Linear Recurrence, keystreams, and periods

I am trying to understand the following problem: Consider the following linear recurrence over $Z_2$ of degree four: $z_{i+4} = (z_{i+3} + z_{i+2} + z_{i+1} + z_{i}) \bmod 2$ i >= 0. ...
30
votes
11answers
6k views

Now that quantum computers have been out for a while, has RSA been cracked?

D-wave systems has released a commercially viable quantum computer. This means in theory, that all asymmetric encryption algorithms — such as RSA — are now useless due to the speed at which quantum ...
0
votes
0answers
42 views

Twofish encryption in Python [closed]

I have a test tool which uses Twofish as the encryption algorithm to encrypt data before sending it to the server. The code is written in C++ and uses Bruce Schneier's optimized C implementation ...
0
votes
1answer
37 views

Bit commitment, two blobs with same bit, without revealing it?

Suppose we have bit commitment scheme: $n=p*q$ and $t \in QNR_n$, with Jacobi $(\frac{t}{n})=1$ Commitment(P), random $x\in \mathbb{Z}_n$, $y=x^2t^b$, where $b$ is bit. Ok, suppose we have $y_1$ and ...
1
vote
1answer
72 views

How does ECDHE_RSA key exchange mechanism work?

Using Wireshark, I found these data exchanged with google.com over TLS: Client Hello possible cipher suites and possible curve types (eg. secp256r1) sent Server Hello cipher suite selected ...
2
votes
0answers
65 views

Is the SEED blockcipher still secure?

I did found an old question which answers exactly this but it is from 2 years ago and i was wondering if there were any changes. I have not been able to find any new information on the cipher and am ...
0
votes
1answer
59 views

Security aspects of using a global values as nonce and additional data for AES?

is it a good idea to use global values as nonce / additional data? What problems can occur? What should be take in account when we deal with such parameters for encryption. Thanks
-1
votes
0answers
44 views

feistel structure? why decryption is so easy with reverse order of subkey

I am doing an assignment on writing own encryption and decryption algorithm..so i come across feistel structure...can someone explain to me why we only use reverse order of key in decrpytion and we ...
7
votes
7answers
2k views

Is it possible to make time-locked encrytion algorithm?

I'm not sure if what I'm asking is even a valid question but here goes. Would it be possible to add a mechanism to an encryption algorithm that would mean it had to be a certain time of the day or a ...
-2
votes
0answers
31 views

Which homomorphic encryption is better for random key generation? [closed]

i am developing an encrypted file using random key homomorphic algorithms which algorithm is best can any one suggest
3
votes
1answer
118 views

Proving the existence of a pseudorandom function

I've been reading the Introduction to Modern Cryptography book by Katz and Lindell as part of my own learning and have come across this exercise which I am not sure how to approach. The exercise is: ...
2
votes
0answers
55 views

Why calculate pi to estimate randomness?

Why do testing suites calculate pi using the Monte Carlo method to determine if a series of numbers are random? As far as I can tell, the Monte Carlo method can be used to estimate pi itself (as a ...
1
vote
1answer
134 views

Is it an example of bilinear pairing?

Consider a bilinear pairing $e: G_1 \times G_2 \rightarrow G_T$. Let's assume, $G_1 = G_2 = G_T = (\mathbb{Z}_n,+)$, i.e. additive group of integer modulo $n$ and $e(x,y) = xy$ mod $n$. Isn't it an ...
-2
votes
0answers
47 views

Credit card number encryption using AES counter mode [duplicate]

I want to encrypt 1000 credit card numbers, and I want do it with AES counter mode. Shall I send the nonce separately and not send it along with ciphertext? Is it possible to use dynamic keys with a ...
4
votes
1answer
204 views

Compact digital signature for noisy data

The question asks for a signature scheme, with a public verification procedure, that is tolerant to minor alterations of the signed data during its transmission [possibly in analog form over some ...
0
votes
0answers
10 views

Paillier algorithm encryption [migrated]

Can any one tell me how to implement paillier algorithm for an file that i am uploading this is my code.. ...
1
vote
2answers
133 views

Is Encryption without knowing the input directly possible at all?

I know the question is rather unusual, but let me clarify what I'm searching for: There is one person, lets call her $Alice$. $Alice$ has $n$ plaintexts $t_1..t_n$ and $n$ public keys $pk_1..pk_n$ of ...
1
vote
2answers
80 views

What is the best hash for HMAC?

Long question but I am starting to lose sight of all the HASH algo's there are. I know SHAKE128 and 256 are part of the SHA-3 standard but is the SHA3 standard officially released yet? i can only ...
-1
votes
0answers
25 views

cryptographic hash function [closed]

Consider an ideal cryptographic hash function H : {0, 1}∗ → {0, 1}n, in other words, H takes a string of arbitrary length and returns a string of n bits, and it is assumed that H acts like a “random ...
-1
votes
1answer
46 views

Should I remove these use cases of MD5/SHA1 from my program?

I have a web app (a register and login system) written already but i am now improving it. One of its design goals was high security. I have some use cases of md5 and sha1 in it and now i am in doubt ...
0
votes
1answer
54 views

Is it safe to use PBEWithMD5AndDES?

I'm encrypting some of my (not so much important) files with PBEWithMD5AndDES. Is it a strong method or it can be de-crypt easily without knowing my selected ...
0
votes
0answers
24 views

Key Confirmation Attack [Key Distribution Center (KDC)]

Okay this is how I understood it according to this: Alice $A$ establishes a connection to $KDC$ and prepares for session key Exchange $k_{ses}$ $A$ encrypts the request with her key $k_A(A, B)$ ...
0
votes
1answer
42 views

Is it safe to encrypt data by simply randomizing chunks based on a permutation?

Say I want to encrypt the following text: "Today is March the 22nd, 2015". And say want to encrypt 8-byte blocks of data using the following permutation [6,3,0,1,5,7,2,4] to swap characters at those ...
-1
votes
1answer
73 views

credit card number encryption using aes-ctr mode

I want to encrypt credit card numbers. I want to apply AES-CTR mode. Is it suitable for that? How can I store nonce and counter values for an individual credit card number? How can I send the ...
0
votes
0answers
31 views

security of pairing based cryptography

while going through some papers on cryptographic accumulators i find the following statement "several pairing-based accumulators have been proposed in the past. However, due to continuous and recent ...
0
votes
1answer
78 views

Why would using a random seed with other variables be bad for ecrypting if you can't guess the key?

I asked this on stack exchange with it being code based, but someone suggested to ask here. Basically, I've done a script in python and wanted an option to encrypt the input, but I couldn't get any ...
0
votes
0answers
8 views

Using ssh agent to sign a string [migrated]

I am trying to learn more about asymmetric keys. I am writing a program that uses ssh-agent server to sign a message. This works well, but it generates a RSA-SHA1 signature of the message, which I am ...
20
votes
3answers
23k views

How can I use SSL/TLS with Perfect Forward Secrecy?

I'm new to the field of cryptography, but I want to make the web a better web by setting up the sites that I host with Perfect Forward Secrecy. I have a list of questions regarding the setup of ...

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