0
votes
0answers
64 views

Is there any pattern in points on EC?

I read some where in crypto.stackexchange answer (related to EC-SRP protocol) that there is pattern in points on elliptic curves, i.e. if given some points containing mix of correct and wrong points ...
0
votes
1answer
38 views

PKCS#7 signed data structure in signed PDF document

Is it mandatory to include PKCS#7 data (OID 1.2.840.113549.1.7.1) octet string into the sequence of PKCS#7 signed data? I mean if you want to sign PDF, you are basically adding PKCS#7 container ...
2
votes
0answers
36 views

During electronic voting, how does one hide the choice from Voting device?

Assume the following: I want to cast a vote during an election through an electronic voting system. For our system we make the assumption that the device one uses to cast the vote is potentially ...
0
votes
0answers
15 views

How are symmetric cryptographic keys stored? [migrated]

If you have a symmetric key which is negotiated via SRP protocol between a mobile device (e.g. smartphone) and a server, what would be a safe way to persist this resulting key on each side? On the ...
-1
votes
1answer
53 views

Openssl library problem

I'm using openssl library and I've a problem with RSA_private_encrypt() and RSA_public_decrypt(). I'm using a key size of 256 bit with no padding of the input message. I've noted that when my input ...
2
votes
1answer
70 views

Is there an existing authorative definition of the cryptographic term 'pepper'

I can attempt to define the term 'pepper' as: In cryptography, a pepper is a something that is added to another value (for example a password) prior to a the value being hashed using a ...
0
votes
0answers
22 views

Device intercommunication with commands

I want to create a smart house project, and in that i bought some simple RF modules. Those modules don't support crypto out of the box but i want to connect them to a device that i would program to ...
1
vote
0answers
38 views

RSA, proof of correct work, if p is not a prime number [duplicate]

Is there any proof of correct work of RSA algorithm, if p is not a prime number? For example: n = p*q, p = p1*p2, where p1 and p2 are primes. Edit: I found that it's called Multiprime RSA, but i ...
2
votes
1answer
90 views

Can Poly1305-AES be used with AES-256?

I'm reading through Bernstein's The Poly1305-AES message-authentication code. The MAC is predicated on 16-byte block ciphers like AES and produces 16-byte authentication tags. However, Bernstein does ...
0
votes
1answer
212 views

Cryptography system by combining a block cipher and a stream cipher

I have to come up with a design for a cryptography system by combining a block cipher and a stream cipher. I can't seem to come up with anything on my own. Can someone point me in the right direction ...
1
vote
2answers
125 views

Prove that if we redefine the key space, we can assume Gen chooses a key uniformly

I am working on problem 2.1 in Introduction to Modern Cryptography 2nd edition by Katz and Lindell. 2.1) Prove that by redefining the key space, we may assume that the key generation algorithm ...
2
votes
1answer
86 views

Stacked LFSR - why not used?

New to cryptographic, weak in math. I have designed a PRG which consist of 33 LFSR's, each 32 bits wide. I use one of the LFSR's as "selector", using the 5 LSB from this register to select one of ...
0
votes
0answers
11 views

Keystore and configuration file

It appears that Java Keystore is often used by web server using a configuration file, with the password opening the JKS written in it and also the password protecting the specific entry. How could ...
0
votes
1answer
61 views

Assemble RSA keys from components

I'm studying openpgp cryptography and struggling to understand some things. I can't use pgp tool for generating keys and ecryption, but have to write a simple app to generate keys, encrypt and decrypt ...
-1
votes
0answers
58 views

In modern definition, what is Enigma, and what caused its downfall?

This question is sparked from the movie The Imitation Game. This single question will have lots of subquestions. The Germans must put the Enigma at the same settings before encrypting and decrypting ...
2
votes
1answer
101 views

Is this a valid scheme to authenticate through a 'human-readable' certificate?

Let's say Alice wants to talk securely to Bob over the internet, and Eve is not only eavesdropping, but has managed to get into a MITM position. In this scheme Alice and Bob exchange $n$ (example $n ...
0
votes
0answers
28 views

Zero knowledge of two factor

Here I overconfident in myself state that I can show, that n has two factors. This is not completely true, can possibly show $n$ is composite - prover generates RSA key with modulo $n$, and gives $e$ ...
2
votes
1answer
969 views

Practical brute-force attack on 128 bit encryption

In brute-force attack calculations cryptographers say we should assume an attacker will find the key after $2^{(n/2)}$ tries. If n=128, then n/2=64. We know that this is practical (A 64 bit key is ...
1
vote
1answer
56 views

Key sizes supported by 3DES

I read about 3DES encryption but I don't understand exactly what the specific meaning of key size is. For example I found that 3DES supports 64, 128, 192, and 256 bits key size. What are all the ...
1
vote
1answer
68 views

Regarding NTRU homomorphic properties

NTRU has some homomorphic properties modulo q, supporting both addition and multiplication. Due to its nature, it cannot support many of them. My main focus currently is in the addition, so the ...
0
votes
1answer
71 views

Collision attacks on digital signatures

After reading this document about MD5 collision attacks, I still don't understand how collisions can make digital signatures insecure. In the paper, the researchers created two files with the same ...
6
votes
1answer
238 views

The effect of truncated hash on entropy

Suppose i have a 128 bits random binary string (128 bits of entropy), then i hash it using SHA-256, then i take the first 128 bits of the output hash. Does the taken bit string still have (almost) 128 ...
-1
votes
0answers
35 views

Can anyone explain how IV(Initial vector ) are chosen in GCM and in CBC MAC in detail?

I actually want to know in detail regarding the IV selection in CBC MAC and in GCM MAC. There is difference in IV between CBC encryption and CBC MAC. Please explain about MAC.
0
votes
0answers
39 views

RSA: If I know n, e, p, and q, how do I calculate d using the extended euclidean algorithm? [duplicate]

After doing a good amount of research, it's become fairly obvious that I ought to be using the extended Euclidean algorithm to calculate d from the data that I already have. However, this isn't an ...
0
votes
0answers
46 views

common ways / methods to try to break a SP network

I have a very little cryptography background (but a relatively solid maths background) so my below question is very general. Basically I have been given a SP network with an output to reverse. I ...
2
votes
1answer
54 views

Is it secure to transmit a short plaintext with its MAC?

I have a short (32-bit) message that needs to be authenticated. Due to the constraints of my platform, I would like to use Speck32/64 (32-bit block, 64-bit key) with a Matyas-Meyer-Oseas one-way ...
4
votes
1answer
147 views

Can machine learning analyze random number generator?

I'm studying for random number generators(RNG) and I saw about machine learning a few days ago. So I searched analysis of RNG using machine learning. But I couldn't find such fields. Are there such ...
1
vote
1answer
78 views

NTRU Encryption

It's using Euclidian inverse. Can you show it step by step? $$N=7, q=11, a = 3+2X^2 -3X^4 +X^6$$ the inverse of $a \pmod {11}$ is $$A=-2+4X+2X^2 +4X^3 -4X^4 +2X^5 -2X^6$$ How do we compute $A$?
0
votes
1answer
58 views

Blum primes [x=3(mod 4)] zero knowledge proof?

Lets say we have 2 primes, $p \equiv q \equiv 3 \pmod{4}$, and we make $n=p \times q$ public. I can, without revealing factors, show that $n$ has two prime factors. How can i zero knowledge prove ...
0
votes
1answer
93 views

Are modes of operation algorithms practical?

I took a cryptography class back in college, and now that I am working my 1st career one of the things currently on my plate is coming up with an algorithm to encrypt data before it's placed on the ...
1
vote
3answers
124 views

zendo data size restrictions

zendo is a new mobile phone app which encrypts messages using a one-time pad: http://techcrunch.com/2015/03/24/one-time-pads-ride-again/ users have to meet in person and exchange a key via a qr ...
1
vote
3answers
92 views

Does perfect secrecy imply uniform ciphertext distribution?

I suspect the answer is no, but I am not able to either prove it, or provide an example. In Katz and Lindell's book, it is only said that with a perfectly secret encryption scheme, the plain and ...
0
votes
1answer
67 views

RSA weak padding

Suppose to have a function for numbers expressed in 8-bit $\in [0,2^8-1]$ defined as: $$f(x)=x||x||x||x$$ where $|f(x)|$ is exactly 32 bits. e.g., suppose x=2 (00000010) so ...
1
vote
3answers
97 views

Cycles in SHA256

In the recommendations, it seems cycles is used usually as in "CPU Cycles", but, that's not what I mean here. What I mean, is this: Let's say I start with a particular 256 bit value. Call this v. I ...
1
vote
2answers
79 views

Hash function such that fx(hash(s1),hash(s2)) = hash(concat(s1,s2))

First, I'm not a mathematician, so I may express this question awkwardly. Feel free to chuckle. I'm wondering if there exists a hash function h such that for given strings s1 and s2, and string ...
1
vote
1answer
61 views

Authentication using a one-time pad

I am building a small embedded system of two nodes that communicate wirelessly. The microcontrollers I'm using are very limited: they only have 256 bytes of RAM. I would like to be able to ...
0
votes
1answer
41 views

Bit commitment, two blobs with same bit, without revealing it?

Suppose we have bit commitment scheme: $n=p*q$ and $t \in QNR_n$, with Jacobi $(\frac{t}{n})=1$ Commitment(P), random $x\in \mathbb{Z}_n$, $y=x^2t^b$, where $b$ is bit. Ok, suppose we have $y_1$ and ...
2
votes
1answer
34 views

Discrete log accumulator without pairings

Here $g$ is some fixed generator of a discrete log group. I don't want the group to be bilinear for efficiency and BDH-skepticism reasons. Is anyone aware of a discrete log accumulator? What I mean ...
2
votes
1answer
101 views

Is the SEED blockcipher still secure?

I did found an old question which answers exactly this but it is from 2 years ago and i was wondering if there were any changes. I have not been able to find any new information on the cipher and am ...
2
votes
0answers
67 views

Why calculate pi to estimate randomness?

Why do testing suites calculate pi using the Monte Carlo method to determine if a series of numbers are random? As far as I can tell, the Monte Carlo method can be used to estimate pi itself (as a ...
1
vote
1answer
94 views

How does ECDHE_RSA key exchange mechanism work?

Using Wireshark, I found these data exchanged with google.com over TLS: Client Hello possible cipher suites and possible curve types (eg. secp256r1) sent Server Hello cipher suite selected ...
2
votes
1answer
154 views

What is this cryptosystem called?

From a paper Outsourcing Large Matrix Inversion Computation to A Public Cloud (IEEE Transactions on Cloud Computing, Vol. 1, N°1, 2013; alternate source requiring registration; preprint), I got to ...
-1
votes
1answer
55 views

Should I remove these use cases of MD5/SHA1 from my program?

I have a web app (a register and login system) written already but i am now improving it. One of its design goals was high security. I have some use cases of md5 and sha1 in it and now i am in doubt ...
1
vote
2answers
110 views

What is the best hash for HMAC?

Long question but I am starting to lose sight of all the HASH algo's there are. I know SHAKE128 and 256 are part of the SHA-3 standard but is the SHA3 standard officially released yet? i can only ...
0
votes
0answers
29 views

Key Confirmation Attack [Key Distribution Center (KDC)]

Okay this is how I understood it according to this: Alice $A$ establishes a connection to $KDC$ and prepares for session key Exchange $k_{ses}$ $A$ encrypts the request with her key $k_A(A, B)$ ...
0
votes
1answer
98 views

Is it safe to use PBEWithMD5AndDES?

I'm encrypting some of my (not so much important) files with PBEWithMD5AndDES. Is it a strong method or it can be de-crypt easily without knowing my selected ...
-1
votes
1answer
92 views

credit card number encryption using aes-ctr mode

I want to encrypt credit card numbers. I want to apply AES-CTR mode. Is it suitable for that? How can I store nonce and counter values for an individual credit card number? How can I send the ...
0
votes
0answers
35 views

security of pairing based cryptography

while going through some papers on cryptographic accumulators i find the following statement "several pairing-based accumulators have been proposed in the past. However, due to continuous and recent ...
1
vote
1answer
63 views

How are RSA and ElGamal compatible in PGP?

I'm starting to play with PGP and I don't understand how if your key pair is RSA you can encrypt a message for someone whose key is for example ElGamal. How does the asymmetric key exchange work if ...
0
votes
1answer
44 views

chaining multiple key derivation functions together

I was looking at PBKDF2, bcrypt and scrypt as options for key derivation; and would like to try using them all together in order to get the cryptographic strength of the strongest one (which seems to ...

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