0
votes
0answers
24 views

transforming RC2 keys to have effective minimum length in implementations with fixed effective lengths

mcrypt's implementation of RC2 has a fixed effective length of 1024 bits, however, it is possible to simulate keys with effective lengths between 1-1024 by doing something like this: ...
0
votes
1answer
42 views

Does SHA-1 hash have quasi commutative property? [closed]

Although I have tested with a program and found negative answer, I want to be sure.
-1
votes
0answers
39 views

Encryption using elliptic curves

What is currently the best way to actually encrypt a message using elliptic curves? I'm looking for an algorithm like ElGamal, but more efficient, since ElGamal outputs a tuple of two points for every ...
7
votes
1answer
126 views

Why there are limitations on using encryption with keys beyond certain length?

I am writing a java program to encrypt a message using 256-bit AES encryption, but I am getting illegal key size error, I have read that I have to use some JCE ...
-1
votes
1answer
53 views

Issue about randomness : what if random looks “human” ? [closed]

I read a lot of stuffs about entropy/randomness. But what if a random generator (either digits or strings) once output a "human" patern ? I know it is very unlikely to happen, but if a random code ...
2
votes
2answers
58 views

Is there an alternative AES schedule?

I'm currently reversing an AES implementation for disk encryption. The odd thing I'm stumbled about is a key schedule where the encryption round keys are not the same as the decryption round keys (in ...
3
votes
3answers
138 views

Verifying DER encoded DSA/ECDSA signature with extra content?

Having a DSA/ECDSA signature which is supposed to be DER encoded as an ASN.1 sequence of $r$ and $s$ (as described in the RFC), and being given some bytes which are ...
1
vote
1answer
50 views

secure embedded/microcontroller crypto using AES-ctr with hmac-sha2

The embedded device is a low-power 8-bit microcontroller (memory usage is constrained to about 10kb code, 1kb ram). As the device is battery-powered and manual service should be minimal, more powerful ...
0
votes
0answers
34 views

Mistakes in Jarecki-Liu use of Camenish-Shoup encryption?

I am implementing a protocol that uses Jarecki-Liu OPRF, which itself uses a simplification of Camenish-Shoup Encryption. Description of the way they do Camenish-Shoup is in section 2.3 of ...
2
votes
1answer
47 views

Finding Elliptical curve points and encoding text using them

I recently got into learning Elliptical curve cryptography and are currently building a project in C#. Everything is working well so far, I can encode and decode points, and thanks to this forum I ...
0
votes
1answer
52 views

How to establish if a string contains a message

If you have a string S, then the string can be composed of four things: cleartext 'random' data encrypted data compressed or otherwise non-encrypted, but modified, cleartext If you want to see if ...
0
votes
1answer
52 views

Does MD5 hash have quasi commutative property? [duplicate]

I am implementing a one-way accumulator using MD5 hash, wondering wheather it has quasi commutative property or not.
7
votes
3answers
410 views

How Brittle Are LCG-Cracking Techniques?

There are published techniques for cracking LCGs, but to my eye those techniques seem very brittle — very minor changes can add nonlinearity that renders techniques like the LLL algorithm unusable. ...
3
votes
2answers
102 views

Collision in Merkle–Damgård without a collision in compression function

Is it possible to find a collision in Merkle–Damgård just by omitting the extra one bit that is appended to each input without having a collision in compression function?
-1
votes
1answer
54 views

Is the Vigenère Cryptosystem malleable? [closed]

Is the Vigenère Cryptosystem malleable, and how can we prove that it is (or it is not) malleable?
0
votes
0answers
6 views

How is security of server's RSA private key is ensured? [migrated]

We repeatedly hear news of hacking of passwords from PW database (server side) but nothing about hacking of server's RSA private key (not asking regarding finding p and q for a given public modulus ...
-1
votes
1answer
59 views

Meaning of Multiplicative Group to the power n i.e. Z^n [closed]

What does $Z_q^n$ mean in this notation?      References: on the 2nd paragraph of page: http://en.wikipedia.org/wiki/Learning_with_errors
1
vote
3answers
126 views

Maximum length in bits of the product n=pq

If p and q are two 1024-bit prime numbers, would the maximum length in bits of product $n=pq$ be ${1024}^2$ or $2^{1024}$? I think it is ${1048576}={1024}^2$? Also, would the least significant bit ...
0
votes
1answer
36 views

can you suggest any applicayion for implementing threshold homomorphic encryption cryptosystem(Paillier cryptosystem) [closed]

I want to implement one project in multi party homomorphic encryption using paillier. Can you suggest any application for implementation.
0
votes
0answers
44 views

RSA OAEP: prevention of partial decryption of ciphertexts

I'm trying to understand RSA encryption (as a beginner in cryptography). go on this wiki page http://en.wikipedia.org/wiki/Optimal_asymmetric_encryption_padding scroll down to the 2 numbered points: ...
0
votes
0answers
30 views

Email Encryption [migrated]

I'm hoping someone can point me in the right direction. If I wanted to implement email encryption within an organisation what would be the best way? I've been searching the web tonight but all my ...
0
votes
3answers
69 views

Repeatedly using same key on different plaintexts

Symmetric encryption: Does using the same key over and over again introduce a vulnerability? Meaning, if I transmit a different piece of plaintext encrypted with the same key every day, will an ...
0
votes
0answers
37 views

Diceware word list for six dice

I really like Diceware, but it now needs six words to be safe. Instead of adding a word, I would think that increasing the size of the wordlist and adding an extra dice would be a better idea. I have ...
3
votes
1answer
71 views

Minimum number of independent trials needed to detect a bias [closed]

Suppose, I suspect that the probability of occurrence of a particular bit as $0$ is $.558$. Since, it is not $.5$, so this is possibly a bias. Now, my question is: What is the minimum number of ...
2
votes
2answers
63 views

Computation indistinguishability questions

The definition I have is: Two probability ensembles $X = \{X_n\}_{n \in \mathbf{N}}$ and $X = \{Y_n\}_{n \in \mathbf{N}}$ are computationally indistinguishable if for every probabilistic ...
-1
votes
1answer
35 views

CoAP authentication using DTLS

what is the meaning of this notation ?? AES{Yi, (Yi XOR Ki | nonce1)} https://tools.ietf.org/html/draft-bhattacharyya-core-coap-lite-auth-00
1
vote
1answer
77 views

Elliptical curve cryptography key generation time

I am currently trying to learn more about Elliptical curve crypthography and have finally started to get things working and undestanding the different pieces. I've written a small project in C# and ...
0
votes
0answers
133 views

Cracking RSA with Small exponent 5

I have read following questions - Cracking an RSA with no padding and very small e Small Encryption Exponent where in first it says to run out all the possible m options and second says factor ...
1
vote
2answers
67 views

Sharing an encrypted file between a group of people

Is there any way to share an encrypted file with a group? In the other words, can I encrypt a file with a public key so that each person in a group decrypt it with his/her private key? Is there any ...
0
votes
0answers
21 views

Wiring pattern for field multiplier

I am doing a project to implement point multiplication unit in elliptic curve cryptography. Going for a galois field multiplier in normal basis. The point multiplication unit is for higher field size ...
1
vote
1answer
42 views

simulating rc4-256 with rc4-128

OpenSSL supports rc4 with 128-bit keys and rc4 with 40-bit keys. It does not support rc4 with 256-bit keys. My question is... is it possible to modify the state of the pseudo-random generation ...
2
votes
1answer
66 views

what are multi-primes and how are they different from semiprimes?

I came to know of semiprimes recently. The simplest explanation of semiprimes is you take any two prime numbers and you multiply them, say 3*11 = 33 in which case 33 would be a semiprime. The numbers ...
-1
votes
1answer
79 views

Cracking plain RSA by factoring the modulus n

This is the setup: I have both public and private keys of one "instance" of RSA. And I have only the public key of another RSA cryptosystem, but this system has the same modulus as the first one. I ...
-2
votes
0answers
33 views

Real life RSA/El Gamal examples

Can someone direct me to examples of El Gamal and RSA that would be similar to real life (i.e. large primes). I wrote a code for encryption and decryption, but I wanted to test it against some larger ...
0
votes
2answers
85 views

Where to store the file extension to retrieve it correctly after decryption

I am using Java to write AES-256 to encrypt various files with different extension, the problem is, where am I suppose to store the file extension so the if the data is decrypted, the file extension ...
1
vote
0answers
79 views

Less known hash functions producing 128 bit hash

Good day. While reversing a malware I stumbled upon a function producing 16 byte hash. I tried to determine which one is that by checking every function from wiki. Nothing fits. So, there are two ...
0
votes
0answers
46 views

Efficient proof of knowledge using Wegman-Carter hash

A verifier wants to ensure, with only little exchange of data with other systems, that a large block of data $M$ that the verifier holds is also available to some other system(s). It is not an ...
0
votes
1answer
75 views

Inverse of a function $f_k(x) := f (x ⊕ k) ⊕ k$

$f : \{0, 1\}^4 → \{0, 1\}^4$ Given a function $f_k(x) := f (x ⊕ k) ⊕ k$, what is the inverse function $f_k^{-1}$? I could not figure out how this would be done. Thanks.
-1
votes
1answer
27 views

El gamal correctness

I tried to find online for the correctness of El-Gamal, but I couldn't find any good resource that will teach me how to show the correctness of El-Gamal, could any body show me how is it done?
2
votes
0answers
93 views

Recovering El Gamal secret key from signatures [duplicate]

Assume out of a set of ElGamal signatures, I've discovered that two have the same y i.e. $signature_{1}$ on $m_{1}$ = $(y,s_{1})$ and $signature_{2}$ on $m_{2}$ = $(y,s_{2})$. The public keys for ...
1
vote
1answer
57 views

What is the difference between IND-CCA2 and NM-CCA2? And how does one imply another? [closed]

Is there any proof that shows the equivalence of these two?
0
votes
0answers
44 views

Mifare Classic and crypto1 algorithm

Mifare's Crypto1 algorithm uses a 48-bit LFSR. What does the 48-bit LFSR do exactly ?
0
votes
0answers
32 views

A rudimentary challenge–response authentication based on dot products in $\mathrm{GF}(2)^k$

We are building a rudimentary challenge–response authentication protocol based on dot products in $\mathrm{GF}(2)^k$. Assume a user has a password $\mathbf{p} \in \mathrm{GF}(2)^k$. When logging in, ...
1
vote
1answer
62 views

Building a pad for OTP on-the-fly with Diffie-Hellman

Through repeated DH attempts, could Alice and Bob build a large random key for use as a one-time pad? My intuition is that this protocol would be as hard as breaking DH (discrete logarithm).
0
votes
0answers
22 views

Recipient ID asked whie using Symmetric encryption with GnuPG [migrated]

I'm trying to encrypt a file using AES algo and sign it using my private key in GPG. The command I'm using is gpg --encrypt --symmetric --cipher-algo aes256 --armor --sign input-file It asks me for ...
1
vote
1answer
71 views

Private Information Retrieval--Is it still theoretical?

Are there any real world products in which private information retrieval techniques are used?(a data hosting server oblivious of which data item was fetched from it?)If not what are the major barriers ...
1
vote
0answers
52 views

Recover a secret message in a .wav file [closed]

First, I apologize for my english, I'll do my best. On my computer, I got a .wav audio file that hides a secret message. I want to recover that message. But I'm stuck and I need your help :). My ...
0
votes
0answers
67 views

How does hash function in Elgamal signature scheme prevent existential forgery attack?

I have heard that hashing the message M prevents an existential forgery attack. I was wondering how.
3
votes
2answers
139 views

Real life systems that use concepts of crypto computing [closed]

Are there any working cloud/internet solutions/products that operates on encrypted data such as systems using homomorphic encryption, secure multiparty computation, electronic voting, private ...
0
votes
1answer
82 views

Addition / Multiplication modulo 13

I am currently studying Diffie-Helman protocol. In my lecture notes I have a generator g=2 and I'm in group $Z_{13}^*$ . There I calculate a remainder cycle from 1 to 12 with $r =g^i \mod 13 \forall ...

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