0
votes
0answers
5 views

How does work Mod operation in Elliptic curve Cryptography

I am developing a program that works with ECC, but I don't know how is it calculated? 1/4 Mod 23=6
0
votes
1answer
26 views

Numeric combination of passwords

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 ...
0
votes
1answer
13 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 ...
-3
votes
0answers
32 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 ...
5
votes
0answers
35 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 ...
0
votes
0answers
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 ...
1
vote
0answers
25 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 ...
0
votes
0answers
13 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: ...
1
vote
1answer
37 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?
0
votes
0answers
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 ...
-1
votes
0answers
30 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.
1
vote
0answers
49 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 ...
1
vote
1answer
36 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 ...
0
votes
0answers
25 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 ...
2
votes
0answers
47 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 ...
2
votes
2answers
14 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 ...
0
votes
1answer
43 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 ...
0
votes
0answers
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 ...
0
votes
0answers
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: ...
0
votes
0answers
22 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 ...
1
vote
1answer
31 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 ...
-1
votes
1answer
61 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.
2
votes
1answer
97 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 ...
1
vote
1answer
54 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 ...
1
vote
1answer
50 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 ...
1
vote
0answers
31 views

Questions about adding 0s to the key in HMAC and how it compares to SHAd

I noticed some strange behaviour when adding different characters onto the end of the key then inputting it into HMAC and I was getting the same output hash. First I generated a key and message to ...
3
votes
0answers
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 ...
1
vote
1answer
40 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 ...
0
votes
0answers
32 views

Encrypting a short phrase into two keys. both with length of 32letters

It doesn't need to be crazy secure. I wanted to figure out if there's a popular practice when encrypting a short phrase (less than 32 letter long) into two keys (two strings 32 length). Doesn't need ...
0
votes
0answers
24 views

What can I change in Lane to

What can I change in Lane to increase memory (and compute) consumption. My first idea would be to change n, but with Lane hash function is there a way I can up the n to a level higher than 512. If I ...
0
votes
0answers
15 views

Cryptography — with a semi-priveleged user in the middle — to prevent request-tampering with another server

I'm working on a chat server for a mobile app I am writing. I would like to use a different application server for non-chat related operations and another application for chat operations. I would ...
1
vote
1answer
41 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 ...
0
votes
1answer
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.
0
votes
0answers
36 views

Nonlinearity of the J-K Flip Flop

In "Encryption Schemes for Computer Confidentiality", Pless describes how to use the J-K flip flop as a nonlinear combiner for linear feedback shift registers. This generator was broken because the ...
1
vote
1answer
123 views

Are the MD5 constants an S-Box?

I noticed that several hash algorithms, in this case MD5, defines some constants. MD5 defines 64 constant values (the shift count per round) which also gets expand (via sine) to a summand for a ...
0
votes
1answer
211 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: ...
3
votes
1answer
106 views

What are the key differences between the draft SHA-3 standard and the Keccak submission?

I just noticed that on the NIST website there is a PDF with a draft of the SHA-3 standard (i.e. FIPS 202) (marked as "new", and seemingly the page was last changed on April 7, 2014). Previously it ...
2
votes
0answers
23 views

Can I prove set membership and uniqueness without revealing the element?

Assuming a publicly known set $\Psi$ with $N$ unique elements. I have a set $\Sigma=\{\sigma_1,\sigma_2,...,\sigma_m\}$ where $m\leqslant N$. I would like to publicly prove that all the elements in ...
0
votes
1answer
58 views

Burn after read algorythm. Software verification on compromised environment. Software smart card

please help me pick right design of software I have to design client-server software, where server should verify that client runs software from exact source code. And where software doesn't simulate ...
5
votes
1answer
255 views

Use cases for CMAC vs. HMAC?

Both can be used to verify the integrity of a message. Assuming you have the needed primitives available to you (i.e. the code space of needing both a cipher and a hash function isn't prohibitive), is ...
1
vote
1answer
55 views

“Fine grain Cross-VM Attacks on Xen and VMware are possible” and OpenSSL 0.9.7

Here's a paper that just made its way into Cryptology ePrint Archive: Fine grain Cross-VM Attacks on Xen and VMware are possible!. Its a good survey of past attacks and presents a couple of new ...
-2
votes
1answer
72 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 ...
0
votes
1answer
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 ...
1
vote
0answers
74 views

Why does computing g^a * g^{-a} with the PBC library result in zero?

My example code is as follows: /* * Example 1 * 1) Calculate g^a * 2) calculate g^{-a} * 3) multiply g^a * g^{-a} * */ Note: here ...
1
vote
1answer
69 views

Definition of one-way functions: randomly-chosen point vs every point

Notation: $\Sigma^k$ is the set of $k$-strings on the alphabet $\Sigma$; $\Sigma^\ast$ is the set of all finite dimensional strings on the alphabet $\Sigma$. In the context of computer-science a ...
3
votes
2answers
122 views

Leaving authentication data blank less secure for AES GCM?

The AES GCM example for Ruby / OpenSSL shown at: http://ruby-doc.org/stdlib-2.0/libdoc/openssl/rdoc/OpenSSL/Cipher.html has a GCM example of the following: ...
3
votes
2answers
79 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 ...
0
votes
1answer
69 views

Is it possible to track down copies of WW2-era codebooks?

I've got an academic curiosity regarding some of the old Japanese naval codes used during World War II specifically, but I was just wondering if any of the codebooks from this era had been made ...
1
vote
1answer
98 views

Usage of different size chunks during AES encryption/decryption

I want to encrypt user's files on our server. For this purpose I decided to use the PHP Mcrypt library. I chose to use the Rijandel-128 algorithm and CBC mode for encryption. Since files are quite ...
0
votes
0answers
41 views

Creating passwords that are both secure and memorable [on hold]

I have seven critical passwords. I want them to be long enough to be secure, memorable enough that I never forget them, unique enough to resist an attacker. How do I achieve this?

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