All Questions

9 views

Why does knowing the number of points on a curve help solve ECCDLP?

Perhaps, this is a really obvious question, but I am still having trouble understanding how this all fits together. Why is knowing the number of points on an Elliptic Curve helpful in cracking it? ...
13 views

Pairings in Identity-based encryption vs. Attribute-based encryption

The bilinear map in Identity-based encryption should satisfy $e(aP,bQ)=e(P,Q)^{a\cdot b}$ whereas Attribute-based encryption schemes use $e(P^a,Q^a)=e(P,Q)^{a\cdot b}$ with $a,b\in\mathbb{Z}_p$ and ...
16 views

symmetrical cryptography [on hold]

In Symmetrical cryptography or private key cryptography we encode our plain text by mangling it with a secret key. Decryption requires knowledge of the same key, and reverses the mangling. ciphertext ...
17 views

difference between leveled FHE and normal FHE scheme

What is/are difference/s between leveled Fully Homomorphic Encryption and normal Fully Homomorphic Encryption?
17 views

DES with actual 7 byte key

Do we have any library or any mechanism where we can use true 7 byte key for DES instead of 8 byte key. I need it for keys analysis in DES and 8 byte key requirement for associated library is creating ...
19 views

Abstract algebra in cryptography [on hold]

I have taken a course in my undergraduate on the theory part of abstract algebra.Now am interested to know how can abstract algebra be applied to cryptography.Thanks
12 views

Timestamping using a hashed linked list and public known events

Let's say we have a timestamping scheme of the following characteristics: The hashes of the documents we are trying to timestamp are xor'ed... ...with "events" whose time of occurrence are very ...
26 views

Is HMAC necessary if the AES ciphertext of a message includes the CRC of the message?

I've seen that encrypting an image with AES-CBC then calculating the HMAC-MD5 value for authentication is a somewhat common and sound way to secure data. Alternatively, can I just calculate the CRC of ...
14 views

How does work Mod operation in Elliptic curve Cryptography [on hold]

I am developing a program that works with ECC, but I don't know how is it calculated? 1/4 Mod 23=6
121 views

Diffusion in Shamir's secret sharing scheme

The popular command line utility ssss implements the classic Shamir's secret sharing scheme over the generic field $GF(2^q)$ with $8 \le q \le 1024$. When $q>=64$, the constant coefficient ($c_0$) ...
32 views

Pls I need explanation on How i can design a Cryptography that use multiple passwords or passphrase to open a safe(Lock). For example, if i need five people to unlock a secured device whereby all the ...
16 views

Do I need two keys for AES CBC and HMAC or can I use the same key for both operations?

I am setting up a Python program to encipher messages on the following basis: -from my password, generate 32-byte key from SHA256(password) -generate a 16-byte IV from a PRNG -measure the length of ...
43 views

The next question about the RSA [on hold]

Let $$n=pq$$ then if $$p^2=n-p\alpha$$ where $$\alpha=q-p$$ why is it impossible to build a smart factorization algorithm even though $\alpha$ is an even number and $p^2$ the only prime squared lower ...
42 views

How secure would HMAC-SHA3 be?

It would be trivial to implement the HMAC construction with (draft) SHA-3, leading to HMAC-SHA3-224, HMAC-SHA3-256, HMAC-SHA3-384, HMAC-SHA3-512 (the last 3 digits are the output size, and half the ...
19 views

Impact of block algorithms parameters on entropy level

I was trying to encrypt some plaintext using different key values with different lengths and trying to understand how this changes make an impact on the entropy level of the cryptogram. However, I ...
14 views

How can I decode a Hill Cipher without a key?

On my exam, we had to solve this problem: message matrix is: [20, 19, 14; 17, 0 10] and the ciphertext matrix is: ...
27 views

Can we parallelize the Feistel Networks?

Classic Feistel Networks and various types of FN's are sequential in nature. [1]has a good overview of different types. But is there a way we can do Feistel Networks in parallel and achieve good ...
45 views

What's the entropy of the output for Tiger Encryption?

I'm tasked to apply tiger encryption to my string(key). Does anyone have any idea how to find the entropy of the hex output by tiger encryption?
53 views

Generalize the Merkle-Damgard construction for any compression function

I am trying to figure out this question: Generalize the Merkle-Damgard construction for any compression func­tion that compresses by at least one bit . You should refer to a general input length ...
21 views

Microsoft CA Certificate Request [migrated]

I am new to MS CA and I have recently installed a MS CA setup on a VM. I used the web service provided "http://test.server.name.tld/certsrv" to request a certificate. I approved my test certificate ...
100 views

State of the art RSA key generation

I would like to know if there is an algorithm to generate a RSA key at the state of the art of the present cryptanalysis. Beside the key lenght I know there are some weakness in the choice of prime ...
33 views

Let N be known and d such that 3d = 1 mod phi(n)

Let N = pq be a product of two distinct primes. Show that if N and an integer d such that 3 · d = 1 mod φ(N ) are known, then it is possible to compute p and q in polynomial time.
38 views

Using beginning of TLS ecnrypted data to reveal secret

I have the following question about TLS security: Assume TLS-PSK protected HTTP with AES256-CBC cipher. When a TLS connection is established, client sends some encrypted data, where the plaintext is ...
26 views

How can compute execution time for generate key AES algorithm? [on hold]

I try compute execution time for encrypt, decrypt and generate key for AES encryption algorithm. I think computed execution time for encrypt and decrypt is correct but I can't compute execution time ...
205 views

Calculating amount of time for brute forcing ciphertext depending on the size of the key

I am a graphic design student and for my information graphic project I have chosen the topic of the history of encryption and how the security level developed over the centuries. It’s basically an ...
980 views

Obtaining the key length from the ciphertext of an auto-encipher

I'm revising for a cryptography exam at the moment and I'm having some problems with a question. The question looks for the key length of a cipher given that the word "earthquake" appears in the ...
50 views

Will hashing over and over eventually give the same hash?

There are many cases in maths where doing the same thing over and over again will bring you closer to a value. Derivation of polynomials is the striking example: no matter what you start with, you end ...
43 views

Spurious keys filter

Is there any possible way to filter a key space in a crypto-system to get a set of keys that decrypts out a valid text (text that is in same language or readable)? I tried a random approach and got ...
32 views

Frequency analysis of transposition ciphers

Can we do frequency analysis of transposition ciphers? If yes, please tell me the procedure and I would be happy if you provide me with some links related to it. I heard that it can be done using ...
162 views

Security of RSA for paranoids with padding?

RSA for Paranoids (RSAP) (in cryptobytes v3n1), also known as Unbalanced RSA, is a variant of RSA proposed in 1995 by Adi Shamir, as a mean to increase the RSA public modulus size while keeping ...
56 views

Cryptography systems based on NP complete problems

There is any cryptography system that have a good reputation based on NP complete problem? I read about the knapsack, but it was cracked.
45 views

How can we prove that two discrete logarithms are equal?

Suppose there are two elements $a = g^x$ and $b = h^x$, where $g$ and $h$ are generators in $Z^*_p$ and $p$ is a large prime. How can we prove that $a$ and $b$ have the same discrete logarithms with ...
79 views

how to use salt to sign a message and how is it effective?

I've had an assignment to sign a file using hash and salt, so I read about salt and I got why it's important when it comes to password, but not to sign messages. How do I sign something using salt? ...
55 views

Which homomorphic encryption scheme has the same size of plaintext space and ciphertext space?

I want to pre-compute the result for all possible ciphertext of a homomorphic encryption. Is it acheivable? Is there a fully homomorphic encryption scheme that has the same size of plaintext space ...
15 views

How to use MSG_MORE and MSG_OOB with AF_ALG while computing hash on a big file? [on hold]

This is regarding the hash computation over a file with AF_ALG from user space. [without OpenSSL] The following link has the mail from Herbert with subject: "RFC: ...
49 views

Key construction in the Full Cramer-Shoup cryptosystem

The Full Cramer-Shoup Encryption scheme needs to choose six random numbers from $\mathbb{Z}_q$, which we denote them by $x_1,x_2,y_1,y_2,z_1,z_2$. Then the scheme hides these random numbers in the ...
255 views

How are private keys stored on disk? [migrated]

I have a public and secret key pair in my .ssh folder. How is the secret key being stored on disk? What I mean is .. Is it possible for someone to hack into my computer, steal the secret key and use ...
9 views

Ruby OpenSSL vs Linux openssl [migrated]

I have a difficulty reconciling Ruby's OpenSSL library with the standard Linux command line openssl. What I'm trying to do here is encrypt the string mysecretstring with the password foobar but first ...
108 views

SSL-like protocol with public-key hard-coded in the client

Imagine a SSL-like protocol that instead of using certificates signed by a trusted CA, has the server's public key hard-coded in the client. My question is: what happens if the server's private key is ...
23 views

ECC Complexity order of point addition, scalar point multiplication and selecting random point

I am facing this problem in calculating the order of a process which involves ECC point addition P+Q , scalar multiplication aP, and selecting random points in the group. the group is of prime order ...
64 views

How can I generate a brief (100) stream of random numbers, not using the computer or throwing dice?

I am looking for a method of making random numbers that is off-line and is also independent of specialist equipment like a Geiger counter.
215 views

CVE-2014-1295 (Apple's Secure Transport and Triple Handshake Attack)

Apple is releasing some updates today. They have not published the bulletins yet, but they are available here: https://gist.github.com/FredericJacobs/11189734. In the writeup for CVE-2014-1295: ...
42 views

HMAC definition by using only one key

Suppose $H$ is a hash function; why is $H(k||H(k||m))$ not secure? See this HMAC definition. In there, indeed two keys are used and the mac algorithm is $H(k_1 ||H(k_2 ||m))$ . Why don't we use ...
81 views

Stateless hash based public key cryptography?

Merkle-Winternitz signatures based on fractal hash trees are an attractive alternative to other post-quantum cryptographic schemes, in particular since they are conceptually simple, the security ...
79 views

Can a zero knowledge proof (or MAC) be generated from human-typable input?

Edit: My goal is to create a voting scheme that doesn't require a lot of crypto infrastructure to be deployed on the client side. Smartcards, and tokens are impractical for these purposes. I ...
242 views

Extracting only the entropy

(I cleaned up the question a bit, It was previously titled "extracting entropy without hashing" .. thus some of the comments / answers) I'd like to extract the entropy of data without injecting ...
55 views

Solving Vignere Encryption

I'm currently trying to crack a cypher that I believe is Vignere Encrypted and I'm currently stuck. I calculated the key length by finding repeated sequences in the cypher and calculating the the ...
73 views

Is less security required for a short stream cipher than for the AES enciphering of very long messages? [on hold]

Criticisms of a cipher system such as 'the ciphertext from one message must be indistinguishable from the ciphertext of a second message" surely only apply when there are very large amounts of ...