2
votes
2answers
5k views

OTP from Sony BIOS password recover

From Dogbert's blog: Sony has a line of laptops ("Vaio") which compete mainly in the high value market segments. They implemented a master password bypass which is rather sane in comparison to the ...
3
votes
2answers
127 views

Real life systems that use concepts of crypto computing [on hold]

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 ...
2
votes
1answer
60 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 ...
-3
votes
1answer
63 views

Is salt bring more security for digital signature! [on hold]

Is it good idea to use salt in digital signature? Is it bring more security? If so, I should use it for key or the message?
-2
votes
0answers
27 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 ...
3
votes
2answers
321 views

Is it possible to match encrypted documents using user-defined search terms?

Suppose I am storing a number of encrypted documents in a database. I would like to make it possible to identify the subset of documents whose contents match user-specified search terms without a) ...
0
votes
0answers
34 views

ElGamal signatures' secret key

Assume I recovered the ElGamal signatures (75,18) and (75,67) Alice produced on the messages 81 and 14, respectively. Alice's public key is (alpha,beta,p)=(2,35,101). How can I recover Alice secret ...
3
votes
3answers
150 views

How can two UProve token holders prove to a 3rd party that they aren't the same user?

Suppose I have two users who are issued two different UProve IDs. The Issuer has guaranteed that one UProve token bearer will never have more than one UProve token ID. How can I use UProve to ...
0
votes
0answers
43 views

Research Path For Searchable Encryption [on hold]

Can anyone give me a list of basic cryptographic primitives and concepts I should know to take up a doctoral research in Searchable Encryption?(If it is impossible to list out, can somebody give links ...
1
vote
0answers
78 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 ...
1
vote
1answer
69 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
1answer
56 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
71 views

Decrypt with only the cipher file and the key? [on hold]

I got an encrypted file, and I got the key. The only thing I don't know is "how it has been encrypted". The cipher file is "data" type (not readable by a text editor), but the key is a "text". Do ...
-1
votes
1answer
22 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?
4
votes
3answers
579 views

How can one sign with NTRU?

I am looking at implementing NTRU, but I noticed that while the encryption/decryption algorithm seems to be mature and well-documented, there is comparatively little information about how to sign ...
0
votes
1answer
72 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.
0
votes
0answers
41 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
0answers
32 views

Feistel network output if round function is the identity function [on hold]

I v been trying to solve this question from the book Introduction to cryptography but fail to find an answer, can someone please explain to me. Thanks What is the output of an r-round Feistel ...
2
votes
2answers
86 views

Large file validation on an embedded system through hash and encryption

As a preface, I have to say that I am a noob in this area. Having said that, I will ask the question. I have a situation where I need to validate and protect against tampering a handful of large ...
0
votes
1answer
68 views

PHP secure random number generator [on hold]

I was trying to find a better way to generate random numbers in PHP and thought that using /dev/urandom would be the way to go (based on a few lectures). So I thought I would implement the following, ...
0
votes
2answers
132 views

Blind Signatures

The verification algorithm given in blind signature. Should it work for both Original message and the signature on it Blinded message and the signature on it. If yes, then how can we verify if ...
1
vote
1answer
55 views

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

Is there any proof that shows the equivalence of these two?
2
votes
2answers
149 views

Zero-knowledge proof of a product

I have non-negative integers $x,y,z$. I'm going to give you commitments $C(x),C(y),C(z)$ to them. Then, I would like to prove in zero knowledge that $xy=z$. I can choose the commitment scheme to ...
4
votes
1answer
112 views

Compact digital signature for noisy data

The question asks for a signature scheme, with a public verification procedure, that is tolerant to minor alterations of the signed data during its transmission [possibly in analog form over some ...
0
votes
0answers
24 views

ECDSA algorithm using PBC library [on hold]

I am doing a project on Identity Based Cryptography.I am doing coding using PBC library. I have a problem in verifying signature .i am using ECDSA algorithm.. can u tell me why signature does not ...
0
votes
0answers
33 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
24 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, ...
0
votes
2answers
110 views

DHE key exchange. Is it really secure?

Context I recently came across a video on the net showing the process of key exchange in Diffie Hellmann. Alice and Bob want to communicate. Eve is the (wo)man in the middle. This video is the ...
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
118 views

Recover plaintext from truncated ciphertext using AES for FPE

I am trying to implement an FPE for a 19-digit long number. I am trying to follow the lecture of Prof. Dan Boneh and here is how I understand it: Get the nearest power of two greater than $10^{19} ...
0
votes
1answer
80 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 ...
0
votes
1answer
76 views

Python. RSA common modulus attack problem

I have: N = /*500 decimal numbers*/ E1 = 3740453 E2 = 4226171 M^E1 = /*500 decimal numbers*/ M^E2 = /*500 decimal numbers*/ I must use RSA common modulus ...
14
votes
7answers
4k views

Types of Cryptography for a 4-8 bit microcontroller

This is more of a research question. I was wondering what types of crypto algorithms would work best on a small 4-8 bit micro controller. I recently read a paper called Security Considerations for ...
1
vote
0answers
38 views

Recover a secret message in a .wav file [on hold]

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
34 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.
6
votes
0answers
113 views

Verbatim of early work on public-key cryptography?

In late 1997, the history of public-key cryptography was turned around with the announcement by the CESG (April 2000 archive) that public-key cryptography was theorized in a 1970 note [1] by James ...
0
votes
0answers
15 views

Change of axis positions in Vigenere Square

Is there any history of codes in which there have been changes in the normal axis positions of the Vigenere Square? Have been working on a code which has two non-normal positions -- one with the ...
1
vote
2answers
345 views

Why we can't implement AES 512 key size?

Out of curiosity why we can't implement AES 512 key size? Please explain somehow i can understand! I'm not an expert.
1
vote
1answer
89 views

Hash collision using the leading 40-bits of SHA-1

I am trying to implement Floyd's cycle finding algorithm for finding a leading 40-bit hash collision in the SHA-1 algorithm. However, my code will not find a repetition even with 800,000,000 hashes. ...
1
vote
2answers
102 views

Encryption of big files in Java with AES/GCM

I have to encrypt big files. Say their size ranges from 500mb to several of gigabytes. I would like to use AES/GCM/NoPadding as provided by Java 1.8 since that gives me automatic authentication and ...
0
votes
1answer
114 views

AES Affine Transformation in $GF(2^4)$

in $GF(2^8)$ the AES affine transformation is defined as \begin{equation*} b( x ) = ( x^7 + x^6 + x^2 + x ) + a ( x )( x^7 + x^6 + x^5 + x^4 + 1) mod (x^8 + 1) \end{equation*} where the polynom $( x^7 ...
1
vote
1answer
70 views

For calculating the index of coincidence for each sequence

I was learning about the finding the key length reading the following web site... http://practicalcryptography.com/cryptanalysis/stochastic-searching/cryptanalysis-vigenere-cipher/ and I really don't ...
2
votes
2answers
166 views

Is there a way to systematically calculate the public exponent $e$ in RSA?

I'm learning RSA in one of my classes and we were given a problem: $p = 5$, $q = 11$ I have done the following steps: $n = 5 \cdot 11 = 55$ $\phi = (5-1)\cdot(11-1) = 40$ I know that to ...
0
votes
1answer
35 views

What Java actually stores inside Keystore when generating Keys?

When we use Keytool to generate a Keystore to store Private/Public keys, what Java actually stores inside the Keystore file ? I ...
0
votes
1answer
62 views

Checking the share membership in secret sharing schemes

I was thinking of this since yesterday. Imagine, a secret is split into its respective shares (using any secret sharing scheme) with threshold $t$ and total $n$. Can we find out given any random ...
2
votes
2answers
241 views

Which attacks are possible against raw/textbook RSA?

The PKCS#1 standard defines multiple padding schemes for signature generation/verification (EMSA-PSS and EMSA-PKCS1-v1_5), and encryption/decryption (EME-OAEP and the less safe EME-PKCS1-v1_5). ...
0
votes
0answers
28 views

java.util.Random and Dice Rolls

For this question, a dice roll will be considered two 6 six sided dice, to give a possible output of 2-12. Given a java.util.Random instance r, the output of one roll would be: ...
0
votes
0answers
19 views

Problem description “SAFE” [closed]

So this is the problem, sorry for the bad img quality. The answer which i don't know is 10 chars long. And there are thease 3 safe knobs with numbers inside them. I have been trying to solve it,yet ...
0
votes
0answers
25 views

Designing hash function in space-efficient identity based encryption

Let $n$ be an RSA-prime and we know prime factorization of $n(=pq)$. The hash function is the current context maps from a given user identity(id) to a positive integer less than $n$, whose jacobi ...
2
votes
1answer
38 views

Committing Bilinear equation in Groth-Sahai framework

Groth-Sahai framework enables us to commit to QE, MSME, PP equations. Now, is the equation below committable in GS framework? A bilinear map $e: G_1 \times G_2 \rightarrow G_T$. $g_1 \in G_1$ and ...

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