2
votes
1answer
68 views

Questions about a SHA3 cipher stream encryption scheme

I have 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 am interested in several things, ...
0
votes
0answers
2 views

Is there any zero-knowledge technique to verify proof of knowledge of shared secret key?

Generally, to verify knowledge/key generated between two interacting parties in an authentication protocol uses Hash, MAC, Digital Signatures or encryption (based on random challenge). But I would ...
3
votes
1answer
429 views

Creating serial key generator using ECDSA, how to get signature short enough?

I've written some questions in this stackoverflow and got great responses but now I'm trying to wrap it all together. I have for the last couple of weeks been building a serial key generator project ...
2
votes
1answer
201 views

Given a linear block-cipher,how can an attacker decrypt any plaintext value encrypted,using 128 chosen ciphertexts

Given the linear block cipher $LinearCipher(k, p) = c$ $$LinearCipher(k, p_1 \oplus p_2) = LinearCipher(k, p_1) \oplus LinearCipher(k, p_2)$$ where $k$ and $p$ are 128-bits. If an attacker uses a ...
0
votes
0answers
10 views

How can I figure out a hash algorithm?

This may be trivial, and may be impossible... this is outside my field but willing to learn. I have a hardware device that accepts a network MAC address (6 bytes of data) like this: 38-60-77-EC-1D-33 ...
8
votes
4answers
2k views

Desirable S-box properties

What desirable properties should an S-box have? My current standard selection process is to just pick them at random and verify that they fit the following criteria: The probability that any random ...
3
votes
1answer
19 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
1answer
87 views

Cracking simple RSA when just the ciphertext and one public key is known

Can someone explain to me (Or better yet, point me to a tool that does the brute forcing) how to crack a standard, simple RSA cipher (So don't bother with padding) if I know just one public key, the ...
1
vote
1answer
12 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 ...
0
votes
2answers
30 views

What is the typical block size in RSA?

If the input text is divided into a fixed block size for encryption and decryption, what could be the typical block size for RSA algorithm for different size of input like 8 MB, 16 MB, 126 MB and 256 ...
7
votes
2answers
618 views

How does hash speed vary based on string length?

Surprisingly I have not been able to find an answer to this question on google. If I have a function that is based on any of the popular hashing algorithms used for password generation, by what ...
2
votes
1answer
138 views

In HMQV, can one use multiple identities with one public key?

The HMQV protocol has 2 "identity" fields $\hat{A}, \hat{B}$ that are used in the dual signature - and it tries to guarantee that any properly-generated session key is only shared by a single $(A, B, ...
0
votes
1answer
53 views

What are coding schemes for timing channels

I know we can hide information in the inter-packet delays, e.g. we can generate a code-book that each code-word corresponds to a message and is generated by realization of a specific random process. ...
0
votes
0answers
11 views

Difference between single-pass and two-pass MACs

I am having trouble understanding where the count of "passes" come in. What constitutes a pass in the context of message authentication codes? How are single-pass MACs achieved?
0
votes
1answer
24 views

Pass a cookie down into an iframe (with 3rd party cookies disabled) through an untrusted domain

Here's an scenario we're running into. Let's say we have: Some untrusted domain, untrusted.com Our trusted domain, ...
0
votes
1answer
12 views

Metrics of PRNGs

I am a bit confused on the metrics that can be applied to the output of (deterministic) pseudo-random number generators. I've run output from many RNGs through ENT. The only metrics that really differ ...
1
vote
0answers
16 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 ...
0
votes
0answers
15 views

Are there known fully homomorphic algorithms that are not secure?

I have a use of fully homomorphic encryption that isn't security based. Are there any known algorithms for fully homomorphic encryption which were discovered and found not to be secure? The simpler ...
3
votes
1answer
136 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?
3
votes
1answer
50 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 ...
1
vote
1answer
101 views

128 Bit AES Issue

I'm trying to use the 128bit TI_aes implementation on my 16bit microcontroller and I'm having the weirdest issue. Every input where two bytes within a word are identical two nibbles within a byte ...
3
votes
1answer
100 views

Public key exponent coprime with totient proof

I read this question a while back (In RSA, why is it important choosing e so that it is coprime to φ(n)?). I was wondering whether there is a proof that shows that a public key exponent e that is ...
0
votes
0answers
37 views

Encrypt/Decrypt cloud passwords with master password

I know it's generally bad to store password in the clouds, and that I should be using salted-hashed password only. I'm making an application that will authenticate a user (with salted-hash), and then ...
1
vote
2answers
55 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 ...
0
votes
0answers
9 views

How often does /dev/urandom sample seeding from /dev/random? [migrated]

Unless I am totally confused and it doesn't do that. I want to know whether or not /dev/urandom will gain increased entropy if I take a hardware RNG and plug its entropy into /dev/random. So to ...
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
votes
0answers
16 views

Differential Side-Channel Analysis on ECDSA

Joyce said assume we have some side channel information like power consumption traces. If we know k = (kl-1,...,k0). And we know biggest bit from k, such as (kl-1,...,kj+1). After that we quess next ...
7
votes
4answers
683 views

Cracking WWII-era codes - code found on a pigeon's leg in Surrey

A recent BBC article entitled WWII code 'may never be cracked' posted a code: AOAKN HVPKD FNFJW YIDDC RQXSR DJHFP GOVFN MIAPX PABUZ WYYNP CMPNW HJRZH NLXKG MEMKK ONOIB AKEEQ WAOTA RBQRH DJOFM TPZEH ...
0
votes
1answer
37 views

What is base of $log$ in Subexponential Algo for DLP?

I am currently going through this paper - "A Subexponential Algorithm for the Discrete Logarithm Problem" by Leonard Adleman. On page 56, author mentions that Dixon's algorithm - Asymptotically Fast ...
5
votes
2answers
240 views
+100

ECDSA signature verifiable 1-way transformations

Alice signs a message $m$ with her private key, yielding a signature ($r$,$s$). I want to prove to someone else that I have this signature, but I don't want them to have the knowledge of what ...
2
votes
2answers
85 views

How to calculate key size of a security algorithm?

There are lots of security algorithms. One of the way to measure security of a cryptography algorithm is to find out its key size. There are many key size of a single algorithm. ECC (Elliptic ...
6
votes
1answer
242 views

Is it OK to use a data-encryption key for key wrapping, too?

Our industry (area of cheap networked devices) has a standard that defines the usage of keys for both authentication and encryption using EAX mode of AES. This standard does not define key management, ...
0
votes
1answer
32 views

Breaking the Rabin Signature system with chosen message attack

I heard that we can break the Rabin Signature system using chosen-message attack. I can't find a message to ask for its signature in order to spoof my message M. Any suggestions?
0
votes
0answers
13 views

Questions about Scyther tool [on hold]

everyone, I want to use Scyther tool to do a project about security protocol analysis but met some problems when I wanted to get familiar with the tool. I used the codes in the Scyther website but ...
-5
votes
0answers
20 views

Progrmaing Language [on hold]

I want to write encryption & decryption programs using ceaser,playfair,vigener,rail fence & monoalphabetic ciphers with c++ language. help me with sites or ideas
7
votes
1answer
196 views

Where is CFB-MAC defined?

I can find descriptions of using CFB mode to create a MAC and even implementations, but cannot find any standard or papers analyzing its security bounds. Is there a standard for CFB-MAC? Where can I ...
0
votes
0answers
30 views

Ways to identify mystery ciphers with no information but the code itself? [duplicate]

I recently offered to solve a cipher that was sent to my friend because he couldn't. I'm really having issues with the identification, I've tried a simple Caesar shift, and it came back with nothing. ...
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 ...
0
votes
0answers
36 views

How to convert the 128 bit output of AES_CTR to 32 bit number? [on hold]

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
vote
2answers
65 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 ...
0
votes
0answers
31 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 ...
3
votes
1answer
72 views

Convert ciphertexts of one encryption scheme to another without decryption

I want to convert ciphertexts of one encryption scheme to another without decrypting them under the first scheme and then encrypting with the second scheme. For example convert OPE encryption to ...
0
votes
1answer
46 views

Are these hash function compositions collision resistant?

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 ...
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 ...
2
votes
4answers
605 views

PRNG taking advantage of very large seed

Can anyone suggest a good (CS)PRNG algorithm that takes advantage of having a very large (ideally arbitrarily large) seed? I'd like to use several kilobytes, perhaps several hundred kilobytes, of ...
2
votes
1answer
31 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
2answers
369 views

Why does WPA2-PSK use 4-way handshake instead of 2-way handshake

I don't seem to grasp why is the handshake for PTK in WPA2-PSK 4-way and not 2-way. Isn't it enough to just have these two steps: First party sends Nonce1 to the other party Second party sends to ...
1
vote
1answer
54 views

What effect does a salt have on attacks against hashes's fundamental properties?

I am interested in analyzing how adding a salt to our hashed passwords affects the three types of attacks we can use. The three types of attacks against hashes are as follows: We have the hashed ...
0
votes
0answers
18 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 ...

15 30 50 per page