0
votes
0answers
3 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
0answers
3 views

How often does /dev/urandom sample seeding from /dev/random?

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
16 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
0answers
5 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
675 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
26 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 ...
4
votes
2answers
198 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
68 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
232 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
0answers
35 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, ...
0
votes
1answer
26 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
9 views

Questions about Scyther tool

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
16 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
194 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
26 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. ...
2
votes
1answer
54 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 ...
3
votes
1answer
101 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
33 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
61 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
28 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
69 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
41 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 ...
0
votes
0answers
58 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 is successfully encrypting ...
1
vote
1answer
22 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
29 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
604 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
27 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
366 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
52 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 ...
14
votes
3answers
2k views

Webcam random number generator

I have a question about random number generators. I have read from a real random number generator, based on a webcam ("randcam"). My problem is, that I do not really understand how the generation of ...
-4
votes
0answers
24 views

I have a challenge for anyone willing [on hold]

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
0answers
33 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 ...
3
votes
1answer
42 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 ...
2
votes
2answers
44 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
18 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
24 views

Gaussian distribution in lattices

In many lattice based cryptosystems, Gaussian distribution is used. Can you explain why only Gaussian distribution is preferred?
0
votes
0answers
12 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
22 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 ...
1
vote
2answers
51 views

Single-algorithm authenticated encryption

Are there any authenticated encryption methods that combine encryption and authentication, rather than useing a separate cipher and MAC?
0
votes
1answer
42 views

How Diffie-Hellman authentication works? [duplicate]

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 ...
8
votes
3answers
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 ...
1
vote
0answers
46 views

Data integrity using steganographic methods

I am looking for a lightweight and fast (almost real time) data integrity checker for a very time critical application. Is it possible to provide data integrity using a steganographic method, lets say ...
3
votes
1answer
41 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
1answer
76 views

How does non-linearity (S-box) add security to AES?

I'm trying to understand how AES guarentees security. One of the named points on the web is that AES uses a non-linear step (the SubBytes step). But how exactly does the Rijndael key schedule add ...
1
vote
0answers
13 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 ...
2
votes
1answer
17 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 ...
1
vote
3answers
129 views

Security of a parallelizable block cipher mode

This is the scheme of a parallelizable block cipher mode of operation: $IV$ is the initialization vector. $BN$ is the zero-based index number of a block in a stream of data. $BT$ is the tweak that ...
9
votes
1answer
4k views

Why do we need Diffie Hellman?

Diffie–Hellman offers secure key exchange only if sides are authenticated. For authentication, sides are using public/private key. So if side A knows the public key of the side B, then A can simply ...
2
votes
1answer
42 views

TLS RSA Certificate with Elliptic Curve Negotiation

When I look at Google's Public Key in Firefox I get PKCS #1 SHA-256 With RSA Encryption Yet according to SSL Labs Google has EC 256 bits / SHA256withRSA and supports ...

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