0
votes
0answers
6 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 ...
0
votes
1answer
14 views

Hash function with iteration and concatenation

If a hash function H is collision resistant, are the following two hash functions collision resistant or not? (|| is concatenation) H'(m) = H(H(m)) || H(m) H''(m) = H(m) || H(m) My first approach ...
0
votes
1answer
9 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: ...
2
votes
1answer
14 views

Why is AES-128 considered secure while RSA needs a 1024-bit size to be considered secure [duplicate]

I got asked this question today and I didn't know the answer, AES-128 is considered secure, the key size is 2^128, so you would need in average 2^127 tries to break the key. Why does RSA need at least ...
0
votes
0answers
15 views

Do most TLS 1.2 implementations express curves in a canonical form when performing EC arithmetic?

Sorry if this is a silly question, but does anyone know if the cryptographic libraries which implement TLS 1.2 for Firefox, Chrome, etc. express a given curve in a canonical form (i.e. one of ...
0
votes
0answers
17 views

Questions about a SHA3 cipher stream encryption scheme

I've written an encryption implementation using a hash as a cipherstream FOR DEMONSTRATION PURPOSES. I know it is slower than more sensible options such as AES but I'm interested in several things, ...
-4
votes
0answers
16 views

I have a challenge for anyone willing

I am incredibly new to the world of cryptography, and perhaps this isn't quite the best site to post on, but I was hoping I could gain insight from some smart minds on my method. I encrypted an ...
1
vote
3answers
22 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 ...
0
votes
0answers
9 views

Extracting key bits from linear cryptanalysis equation for SDES

From the linear cryptanalysis of SDES, we get a linear equation consisting the K[1, 3] of the round key 1 and 2. From this how will I retrieve the key bit? How do we solve the linear equation we get ...
0
votes
1answer
15 views

Vulnerabilities in specifying the hash algorithm used for signature verification on a per-message basis

Let's say that I have a 4096-bit RSA key and when I sign data, I typically use SHA-512. As far as I understand it, the hash algorithm used to sign/verify a message is specified in the message. If a ...
0
votes
0answers
11 views

How are the attributes of a user authenticated in attribute-based encryption?

It seems that the papers I am reading do not talk much about this point. That is how the attributes of a user are authenticated in ABE system. To my understanding, there is an attribute authority ...
0
votes
1answer
16 views

How is the root certificate transmitted to pc?

i understand that the purpose of root certificates and CA's is to ensure that the communication parties are who they say they are. But how is the root certificate acquired? Is it not possible that ...
0
votes
0answers
31 views

Convert one encryption scheme to another without decryption

I want to convert one encryption scheme to another without decrypting the first scheme and then encrypting with the second scheme. For example convert OPE encryption to Paillier without decryption. ...
2
votes
2answers
38 views

How can we define division operation by using Fully homomorphic encryption

Last fews months, I'm working with homomorphic encryption. Now I am dealing with some computational problems with integers or real-numbers (like arithmetic mean, standard deviation) where division is ...
0
votes
1answer
38 views

How Diffie-Hellman authentication works?

There are a lot of good videos on a simple Diffie-Hellman in the internet but unfortunately that is susceptible to the MITM attack. I understand how with DH the two parties are able to calculate a ...
0
votes
0answers
30 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 ...
0
votes
0answers
22 views

Gaussian distribution in lattices

In many lattice based cryptosystems, Gaussian distribution is used. Can you explain why only Gaussian distribution is preferred?
2
votes
1answer
16 views

What does the probability subscript mean in Shannon's secrecy definition?

Shannon's secrecy can be defined as: $$P_M (M=m) = P_{SK,M}(M=m|E(SK,m)=c)$$ What does $P_M$ means? (same question for $P_{SK,M}$) I know that is the probability space M, M being the messages; I do ...
2
votes
0answers
9 views

What happens to NORX if the same (key, nonce, header data) triple is reused

As I understand it, reusing a (key, nonce, header data) triple in NORX leaks the XOR of the initial common prefix (but this is zero, so only its length is leaked) the XOR of the first distinct ...
0
votes
0answers
28 views

Fast hash for 64-bit inputs

I am looking for a fast hash (~few machine instructions) to be used for hash tables with 64-bit keys. I can't use SipHash as the hash function will be inlined in too many places and so the code size ...
2
votes
1answer
34 views

How to design a deliberately weak PRNG for experimentation?

I'm looking for a PRNG that is deliberately weak, that is, follows a set of rules stochasticly. For example: Encounters a set of bits that is a multiple of X, starts exhibiting bias, or starts to ...
0
votes
0answers
21 views

Dieharder text file for output of AES_CTR

I want to run Dieharder test suite on the output of AES_CTR. How should I form the text file consisting of the cipher text obtained from AES_CTR, to be run directly with Dieharder package for linux?
-1
votes
1answer
63 views

RSA private key finding method

Bob uses RSA with $p=83$ and $q=103$. His public key is $e=445$. Alice claims that she can calculate Bob's private key without using the definition $d=e^{−1}\bmod φ(n)$? But how?
0
votes
0answers
20 views

why OCB over AES for authentication encryption?

why should anyone use OCB-offset code book over AES algorithm?
0
votes
1answer
22 views

Determining collision resistance of a function?

I am having trouble trying to understand if the function is collision resistant. As I understand it, preimage resistance means that it is hard for an adversary to find two messages that produce the ...
1
vote
0answers
12 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 ...
0
votes
1answer
15 views

Multi Authority Attribute Based Encryption Library

Anyone aware of a library that has MA-ABE implemented in any language preferably python? P/S - I hope this is the right place to ask this. Apologies if not, then a redirect will be appreciated
3
votes
1answer
37 views

The sign of the correlation in linear approximation

${\text{Let }}g:{\{ 0,1\} ^n} \to {\{ 0,1\} ^n}$ be a round function of an $n$-bit iterated block cipher and let $K \in {\{ 0,1\} ^n}$ be a fixed round-key, and denote ${g_K}(x) = g(x \oplus K).$ Show ...
0
votes
0answers
24 views

Have ciphertext and key but need to figure out encryption method

So I have a block cipher (I think) that I need to break. I have the ciphertext and the key, but not the method of encryption, and was wondering if anyone could help me figure that out? The key is a 9 ...
0
votes
0answers
29 views

AES Twofish Serpent

AES-Twofish-Serpent how to create this combo encryption? I am using Linux Mint and i want to encrypt few big folders in one folder, but to be hiden.
-1
votes
0answers
15 views

M3 Bitlocker Recovery

Has anyone used this software? Is this a legitiamate solution? I am working on rolling out bitlocker encryption on some devices and I want to have a data recovery plan in place. I am looking for ...
-1
votes
0answers
29 views

What kind of obfuscation is used in this image? [on hold]

Edit: This is not off topic since I am not requesting analyzing or deciphering a block of data here. I'm NOT asking anyone to solve this, I'm looking for the name of the obfuscation technique used ...
1
vote
1answer
17 views

OpenSSL & TLS1.2 with aes-cbc and initialization vector

I'm trying to manually decrypt DTLS traffic using OpenSSL and TLS 1.2. The cipher suite im using is AES256-SHA256 as listed here. Im able to decrypt the packets with the key that the server and the ...
0
votes
3answers
83 views

How is a message digest decrypted?

Trying to get my head around digital signatures and hit a slight block. The book I am using gives the following information Device A hashes a message to create a message digest Device A encrypts ...
0
votes
0answers
32 views

What are the pre-requisites I need to be able to code Salsa20 in C#?

I've taken a basic course in Cryptography and we've learnt various algorithms and their usage. I've implemented RC4 and Triple DES in C# with ASP.NET. For a project that I am a part of, I need to ...
1
vote
1answer
45 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 ...
4
votes
2answers
52 views

Is reusing keys for CBC and CBC-MAC secure when using encrypt-then-MAC?

I know reusing keys is a bad idea, especially for CBC and CBC-MAC, but the example for why on Wikipedia seemed to use encrypt-and-MAC. It seems obvious that the last block of encryption will be equal ...
1
vote
2answers
37 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 ...
0
votes
2answers
32 views

What is the time requirement for pairing computation and modular exponentiation?

I want to design a cryptographic protocol for encrypted search without pairing. I have seen some papers for protocols without pairing. How would I compare pairing computation and modular operations?
1
vote
1answer
56 views

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

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 ...
-2
votes
0answers
13 views

Please help me decrypt this Classical Cipher [on hold]

Can any one help me decrypt this message: noohaiisee spyg iOyh h ol ceet pbcuoonnss
0
votes
0answers
10 views

How do you apply bilinear mapping to attribute based encryption?

I'm new to both bilinear mapping and ABE. I have a vague idea of how bilinear mapping works now, but I don't understand how it applies to ABE. Can someone give me an example?
1
vote
0answers
19 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
votes
1answer
22 views

Need CryptDeriveKey AES implementation in C#

I am integrating with 3rd party software that uses AES 128 encryption. I know this is not ideal, but the choice of encryption is up to the 3rd party software. I am using C#. My problem is in deriving ...
0
votes
0answers
25 views

Permuted Hash Table

Suppose we have a hash table, $HT$, consisting of $100$ bins.The hash table uses a hash function $H$ that is public. We all know that given value $a$ we can compute the address in the hash by ...
0
votes
0answers
26 views

Interesting Topics for Projects?

I hope this is not a off-topic question for the site, but I was wondering if I could get any recommendations for project topics in cryptography suitable for someone just learning basic material now. ...
0
votes
0answers
25 views

How to create Crypto based Project

I took Cryptography course last semester and It was very interesting. To have a more practical understanding, I thought I should create a mini project. Below is the ...
0
votes
0answers
23 views

Poly1305 vs VMAC: is VMAC much better for long messages?

VMAC seems to me much more secure than Poly1305 on long messages (the security of the latter decreases linearly with increasing message length). Is this of practical relevance?
0
votes
1answer
40 views

AES128 Decryption in Objective-C just slightly off

I have been asked to integrate a home-grown CRM system with a 3rd-party data service provider (DSP). The DSP has encrypted the information they are providing. I only have their decryption ...

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