0
votes
1answer
92 views

New to cryptology, studying key exchange

I'm just getting an overview of some of the concepts in key exchanging at the moment, and I'm a bit disoriented on a few topics, namely key stretching, key derivation functions and perfect forward ...
1
vote
2answers
143 views

Is computing roots moduli a composite $N$ a hard problem without knowing the factorization of $N$?

Suppose that we are given $\mathbb{Z}_{N}$ and an element $x^u \in \mathbb{Z}_{N}$ with $u \in (0,l]$ where $l$ is the bit-size of $N$. Is it difficult to recover $x$ by knowing $u$ without knowing ...
3
votes
1answer
86 views

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

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 ...
1
vote
0answers
82 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 ...
3
votes
1answer
332 views

Is only one shared secret generated by ECDH per key pair?

I'm confused about ECDH. Using their public keys and private keys, two entities can arrive on a shared secret. But from the equations I've seen, it looks like ONLY the numbers present in their key ...
13
votes
1answer
617 views

Choice of multiplication polynomial in Rijndael s-box affine mapping

The Rijndael specification details the design choices for the s-box in section 7.2. They describe the choice of affine mapping as follows: We have chosen an affine mapping that has a very simple ...
-1
votes
1answer
213 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 ...
3
votes
3answers
827 views

Searching over encrypted data [duplicate]

Is there any library/tool available which can allow me to search over encrypted data? I would like to encrypt data on client side, send it to cloud and perform search in cloud. I've been reading ...
2
votes
1answer
107 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 =...
2
votes
0answers
39 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
2answers
102 views

Would the Fiat Shamir identification scheme be more secure if I design it with an exponents higher than 2?

Let's say both Prover and Verifier would use nth power instead of 2nd when creating public keys and when verifying. I know it would slow it down but would that cause the protocol to be more secure?
1
vote
1answer
162 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 ...
4
votes
1answer
220 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 ...
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
166 views

What kind of Quantum cryptography technology(protocols) can be used for Mobile Ad hoc networks(MANETS)?

Typically ad hoc networks do not have a proper infrastructure and the routing is done only through the base stations which are connecting a wired and wireless network. Does quantum cryptography ...
2
votes
1answer
120 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 ...
2
votes
2answers
386 views

Which characters to take into account when calculating unicity distance?

I need to calculate the unicity distance of a block cipher. Assuming I know that the plaintext is an English message I considered using 53 as the size of the alphabet, since the message could contain ...
1
vote
1answer
151 views

Of what use is my code for finding prime numbers of a certain size?

I've developed a bit of Mathematica code that can find primes within a range of numbers. For example, if I wanted all the primes between one million and two million, it could do that. Of what use is ...
2
votes
1answer
117 views

What aspect of elliptic curve encryption paradigms makes them especially susceptible to quantum based attack algorithms?

This was a statement made during a talk at today's DFN-CERT conference but unfortunately it wasn't explained further. Can anyone shed light on why elliptic curves are susceptible to quantum based ...
2
votes
1answer
1k 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 ...
0
votes
1answer
310 views

Difference between the TLS cipher suites?

TLS_DHE_DSS_AES256_CBC_MAC / TLS_DHE_RSA_AES256_CBC_MAC Hi, I have been studying to learn about various cipher suites and their performances. I gathered that DSS is efficient when compared with RSA. ...
1
vote
0answers
73 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
4k 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 ...
0
votes
0answers
42 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
64 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
80 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 ...
1
vote
1answer
154 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 $A$?
1
vote
3answers
321 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 ...
2
votes
1answer
59 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 ...
0
votes
1answer
95 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 ...
2
votes
3answers
218 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 ...
0
votes
1answer
97 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 ...
0
votes
1answer
83 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 $f(x)=2+2^9+2^{17}+2^{25}=...
1
vote
1answer
133 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 ...
2
votes
1answer
169 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 ...
0
votes
1answer
60 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 ...
4
votes
1answer
385 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 ...
1
vote
2answers
870 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
1answer
167 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 ...
0
votes
1answer
61 views

Is it safe to encrypt data by simply randomizing chunks based on a permutation?

Say I want to encrypt the following text: "Today is March the 22nd, 2015". And say want to encrypt 8-byte blocks of data using the following permutation [6,3,0,1,5,7,2,4] to swap characters at those ...
-1
votes
1answer
199 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
1answer
176 views

Why would using a random seed with other variables be bad for ecrypting if you can't guess the key?

I asked this on stack exchange with it being code based, but someone suggested to ask here. Basically, I've done a script in python and wanted an option to encrypt the input, but I couldn't get any ...
22
votes
3answers
33k views

How can I use SSL/TLS with Perfect Forward Secrecy?

I'm new to the field of cryptography, but I want to make the web a better web by setting up the sites that I host with Perfect Forward Secrecy. I have a list of questions regarding the setup of ...
1
vote
1answer
145 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 ...
2
votes
3answers
527 views

SHA-1:Is there any mathematical result that gives us the minimum number of 1's in a 160-bit SHA-1 hash output?

Is there any mathematical result that gives us the minimum number of 1's in a 160-bit SHA-1 hash output? What is the probability that a 160-bit SHA-1 hash output contains at least 128 1's?
1
vote
1answer
119 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 ...
0
votes
1answer
223 views

How do you implement a cipher as one lookup table?

I am reading up on whitebox cryptography and have trouble understanding how are ciphers implemented as one lookup table? assuming my plaintext is just 4 bits so the size of my lookup table should be ...
0
votes
2answers
414 views

Practical Attack on RSA

Currently I am designing an RSA based application, and I am thinking of how long should the key be in order to be secure against attacks. I know that RSA 4096 bit key can be recovered using Sound ...
5
votes
1answer
428 views

Purpose of expanding then shrinking in SHA-1

What is the purpose of expanding then shrinking in SHA-1? Does it serves any security purposes?
1
vote
1answer
237 views

Replacing the PRF in PBKDF2 with Keccak

I am unable to find a reliable, tested library for a decent password based key derivation function e.g. Scrypt in the programming language I am using, but I have a reliable library for PBKDF2 (which ...

15 30 50 per page