1
vote
1answer
44 views

Tackling encryption problems with “Zipf's law”?

I am new to cryptography and was wondering if it would be possible to semi-reliably "decrypt" an encrypted message by using the statistical distribution of symbols (/letters/numbers) in the encrypted ...
-4
votes
0answers
15 views

Autokey Cipher Question [closed]

you receive the message DQIXFQETXPPZZR Given that the ciphertext has been encrypted using an Autokey cipher with key k in the range 16 to 18, decipher the meassage. Thanks,
0
votes
0answers
18 views

Why does DSA require that a new $k$ be chosen and the algorithm restarted if $s=0$?

DSA is an algorithm used to generate a digital signature, which consists of a pair of values $(r,s)$. The algorithm computes $r$ first and then $s$. However, if we calculate $s=0$, it says to restart ...
1
vote
1answer
32 views

how to prove sequence y uphold golomb's third axiom

given $\{ x_k \}$ is a m-seq of order $n$, we define $\{ y_k \}$ to be a $m$ digits number: $$ y_i=x_ix_{i+1}...x_{i+m-1} $$ for every integer $n \ge m \ge 1$ how can I show that $\{ y_k \}$ upholds ...
1
vote
0answers
33 views

How to use OpenSSL command line utility to encrypt data with encrypted key from public key?

I may not be asking the right question. I am fairly new to data encryption. I am currently being sent encrypted data that's stored as follows: [ [keysize] [key encrypted with public key] [ivsize] ...
5
votes
1answer
91 views

Key size for HMAC-SHA256 [duplicate]

After reading a bunch of past stack exchange posts like this one and RFCs 5869, 2104, and 4868 I felt comfortable that a 32-byte key was sufficient for HMAC-SHA256. However, I am implementing my code ...
3
votes
0answers
30 views

EC Schnorr signature: multiple standard?

I 'm working on some EC-Schnorr signature code. Reading various papers on that, it's seems EC-Schnorr is not standardized as well as ECDSA. For example, I found two main differences in two main ...
1
vote
1answer
2k views

Traditional DES scheme in Unix crypt function

In a security context course, we need to reproduce the old DES hashing scheme in the crypt program, on an old unix system. I am actually reading the crypt page on wikipedia: The traditional ...
-1
votes
0answers
65 views

How to prove that twice the application of a secure PRF stays secure? [closed]

Problem 4.6*: Let $E: \{0,1\}^k \times \{0,1\}^l \rightarrow \{0,1\}^l$ be a block cipher. The two-fold cascade of $E$ is the blockcipher $E^{(2)}: \{0,1\}^{2k} \times \{0,1\}^l \rightarrow ...
5
votes
3answers
130 views

Searchable Encryption with Substring Search

I want to search substrings in encrypted string. To do that I have read “Implement Rabin-Karp Algorithm” and “Substring-Searchable Symmetric Encryption”. After that, I completed the Rabin-Karp ...
1
vote
3answers
107 views

with RSA encryption, how do I find the md5sum of the private key from the public key?

This is a purely mathematical question on RSA encryption. Having $e$ as the public key exponent and $n$ the modulus of a public key. Can I recover the md5sum of the private key $d$ (inverse of $d$ ...
0
votes
1answer
52 views

Give a simple hash chain example in Java [closed]

I am looking for a very simple example of cryptography hash chain source code. Could you forward me some examples or link, guys? For example, https://en.wikipedia.org/wiki/Hash_chain [1]. ...
3
votes
2answers
341 views

Why is “multiplying” $g^x$ and $g^y$ not possible?

The computational Diffie-Hellman problem states that for a cyclic group $G$ of order $p$ and a generator $g$, it is hard to find the value $g^{xy}$ given only $g^x$ and $g^y$ (but easy if either $x$ ...
0
votes
1answer
148 views

In RSA. Why is $\phi(n)$ kept secret and $n$ is public?

I mean, $n$ can also be easily used to find the factors $p$ and $q$ right?
-1
votes
0answers
24 views

Denial of service using Merkel tree proof

If suppose client and server using Merkel tree and some how Server got compromised, what he can do is always send wrong proof therefore denial of service. Is it as simple?
5
votes
1answer
205 views

Authentication by hardcoding public key in client software

It would seem to me that mobile applications could reduce network traffic by hardcoding the server's public key into the app. The idea being that they could then encipher a secret to share with the ...
0
votes
0answers
24 views

Using a straight password for encryption and authentication

Assume we have a password like 3buNCh_7kaRmencrEst3. Now suppose we have two parties who know this password. We a have communication scheme that uses the password ...
0
votes
0answers
23 views

Is there a function that can be used to satisfy collision resistant property in MAC? [on hold]

I am doing a project in cryptography where i need to satisfy collision resistant property in my MAC algorithm, is there any function that can be used in MAC that already satisfies collision resistance ...
3
votes
1answer
85 views

Is there any function that does not suffers birthday problem?

I am eager to know that if there is any function that does not suffer birthday problem and how to prove it formally that the function is not suffering the birthday problem.
0
votes
0answers
24 views

MAC is constructed by hashing and then encrypting

Suppose the MAC is constructed by hashing and then encrypting, that is $MAC(m, k2)=E_{k2}(H(m))$ where H is a public hash function. There can be several alternatives in how the transmitted message is ...
3
votes
0answers
20 views

About BGV Scheme Batching Technique

I am reading BGV12 about BGV homomorphic scheme right now.But I am being stuck to understand Batching technique in this paper. In Pack function (page 32),this paper feeds ciphertext $c_i$ and sk ...
0
votes
0answers
10 views

Using Openssl Libarary to convert .key encoded to .pem [migrated]

So i created a c program that takes in an encrypted (encrypted.key) file and a public key to decrypt the private encrypted encrypted.key. However, my program only works when taking in two files that ...
3
votes
2answers
265 views

PGP String-to-Key specifiers

I've been reading through the PGP Standard and here I'm a little confused. This section is discussing converting string data to a session key. I'm confused about the paragraph in bold. First off, what ...
1
vote
2answers
43 views

Key management and derivation - Allow changing of the passphrase

I'm working on a program, which allows encrypting files before storing it on a cloud service. Currently I'm trying to figure out how to derive and store the keys. First, I wanted to use a simple ...
3
votes
0answers
53 views

When to chose hardware accelerated crypto for Big Data

if you were to recommend a cipher/mode configuration that emphasizes performance for your customers, would you recommend a hardware based accelerated solution over one that isn't? For big data at ...
1
vote
1answer
64 views

Analysis of DGHV Security

I want to know how security of DGHV can be breached using oracle and Binary GCD. As I study this paper : Fully Homomorphic Encryption over the Integers But I am not able to understand Section 4.1: ...
-3
votes
1answer
85 views

RSA when n= 2360221 and encryption = 5 find decryption key d, when M =1234

when n= 2360221 and encryption = 5 find decryption key d,and Cipher text C when M =1234
1
vote
2answers
60 views

Initializing PGP keys by one side

I am using a PGP method to encrypt and decrypt messages shared between users A and B. Upon the start of a message exchange is the initialization of the public and secret keys by both Users. Lets say ...
5
votes
2answers
193 views

Trapdoor and RSA (Schneier)

Disclaimer: I'm new to cryptography. Background: From Applied Cryptography (Bruce Schneier), page 30 of 2nd edition A trapdoor one-way function is a special type of one-way function, one with a ...
1
vote
2answers
156 views

Modular Multiplicative Inverse and RSA?

In trying to understand this specific part of the RSA algorithm, I found this online: $$e \cdot d = 1 \pmod{(p-1)\cdot(q-1)}$$ Therefore: $$e \cdot d \cdot d^{-1}= d^{-1} \cdot 1 ...
2
votes
1answer
35 views

What implementation properties of a hash function prevent safe truncation? [duplicate]

Truncating a hash function's output should, in theory, not increase the likelihood of a collision more than you would expect based on the truncated output size. This makes sense when thinking about ...
3
votes
1answer
60 views

What are the time considerations with regard to security against birthday attack?

When designing security for a physical safe, one of the critical specifications is how long will the safe resist attack, this tells you how quickly you must detect and respond to an attack on the ...
3
votes
1answer
112 views

Why only one secret value with Shamir's secret sharing? [duplicate]

Shamir's Secret Sharing works by sharing data points on a curve, whereby when you have the required number of data points, you can find the function of the curve and find out the secret, which is ...
2
votes
1answer
62 views

How to detect what crypto-method is used by Filecoder.Q?

I have 2 different images, one original, and one locked by a malware detected by eset as "Win32/Filecoder.Q". How to detect the encryption method that is used and the key, that is not using any ...
0
votes
0answers
14 views

Testing the first 40 bit sequence for A5/1 if all registers initialized to 1

I have an assignment where my instructor asked to generate the first 40 bits for an A5/1 algorithm if all registers are initialized to '1' initially . I have implemented the algorithm successfully ...
1
vote
0answers
48 views

Does using a verifiable secret sharing scheme ensure robustness of a protocol if it is secure under the semi-honest adversarial model

Consider a protocol $\pi$ which uses a linear secret sharing scheme like that of Shamir secret sharing. Further assume that the protocol $\pi$ has been proven to be secure (correctness and privacy) ...
1
vote
1answer
42 views

What would be a typical value for the security parameter of the Fully Homomorphic Encryption over the Integers scheme?

The parameters of the Fully Homomorphic Encryption scheme by Dijk et.al are chosen according to the value of the security parameter ${\lambda}$, section 3 of the aforementioned article. What is the ...
0
votes
1answer
34 views

Synchronous Stream Cipher Problem

Hello I am facing a problem trying to solve this question in the picture. Does anyone know how to produce the mentioned 32-bits of the key stream? The plaintext in this case is ...
3
votes
1answer
98 views

Trying to understand textbook exercise question regrading RSA

I am preparing for the final exam in my Data Security class so I am trying to read and understand the textbook's exercise questions. Any hint would be great. Question (Exercise 9.14 of textbook): ...
5
votes
1answer
176 views

Finding the subgroup in isogeny-based cryptography

Isogeny-based cryptography is one of the newest post-quantum cryptography. Hardness of this system is based on finding isogeny between two elliptic curves. Also this is theorem: Elliptic curves ...
3
votes
1answer
41 views

About ORAM initalization and running out of space

I have two questions about ORAM Since at the beginning,the server allocates unused storage for ORAM cient,there are no user's data in the storage.if now client access the storage the server will ...
4
votes
1answer
169 views

Full encryption of IDs, partial decryption with customer specific key

I am looking for a "partial" encryption/decryption algorithm. Let's say I am encrypting the following List of IDs (long values) $[1,2,3,4]$ (with a secret key) to an encrypted string $e$, I would ...
2
votes
2answers
139 views

System parameters in identity-based encryption

In IBE schemes, the system parameters are $(q, \mathbb{G}, F, \hat{e}, P, Q, T, H_1)$. I don't know $\hat{e}$. For example, in type A pairing… ...
7
votes
0answers
209 views

Are there any practical attacks that create a printable chosen prefix MD5 collision?

I would like to create two ASCII text messages with the same MD5. Is this possible? If not, is there a similar but less strict attack that could work? Or to rephrase my last question: what are the ...
1
vote
1answer
57 views

what is meaning of operator “ := ” in cryptography?

I've seen := used in several cryptography papers where the this symbol has been used instead of assignment operator ($ \leftarrow $ ) or equal sign (=), but never with an accompanying explanation. ...
0
votes
1answer
44 views

Are collision-resistant hash functions even possible? [see description] [duplicate]

Surely there can be no real collision resistant Hash function since hash values are of finite size which means there are finitely many of them, but there are an infinite number of messages we could ...
15
votes
3answers
9k views

What are preimage resistance and collision resistance, and how can the lack thereof be exploited?

What is "preimage resistance", and how can the lack thereof be exploited? How is this different from collision resistance, and are there any known preimage attacks that would be considered feasible?
0
votes
0answers
40 views

signature, hashing schemes

I have 20 friends. we create message(s) (1...i) and tar them up with a file messages.hashes(1..i). We sign these tars with our ...
0
votes
0answers
38 views

Find SHA256(secret||data) using SHA256(secret) and data

I need to find the SHA256 hash of s string like this: "part1-part2". I know the SHA256(part1), length of part1 and I know part2, but I don't know what is the contents of part1. Is there any chance I ...
0
votes
0answers
26 views

What is transaction capacity of a POS using 3DES DUKPT?

I am looking for the transaction capacity of a Point-Of-Sale device using 3DES DUKPT. Once all keys derived from the future key set are exhausted (1M or 500K?), how will the POS be reloaded with a new ...

15 30 50 per page