All Questions

0answers
32 views

How about a homomorphic integer sorting in a MPC context?

I want to implement the ATV-FHE scheme as described by Adriana López-Alt, Eran Tromer, Vinod Vaikuntanathan: On-the-Fly Multiparty Computation on the Cloud via Multikey Fully Homomorphic Encryption ...
0answers
39 views

How to verify a signature with openssl methods from the ECDSA class?

I'm trying to verify my signature like I explained in my question before. But I have some problems to program my own verification without the verify methods of openssl. Therefore I'm going on to use ...
1answer
37 views

Truncating ciphertexts on ring-LWE schemes

On the section 5.4 of the paper Improved Security for a Ring-Based Fully Homomorphic Encryption Scheme, the authors explain how to discard some bits of the ciphertexts to get smaller ciphertexts and ...
1answer
58 views

Can Pseudorandom values be used as secure keys?

I want to derive $n$ keys from a master key. I pick a master key $mk$ and use pseudo-random function (PRF) to generate $n$ pseudo-random values, $v_i=PRF(mk,i)$ where $1\leq i \leq n$. Next, I use ...
0answers
54 views

Brute force attack multiple stream cipher

Assume that a scheme used to secure a specific system $Π=(Gen,Enc,Dec)$ which is thought have indistinguishable multiple encryption in the presence of an eavesdropper. For any adversary $A$ that can ...
0answers
33 views

How does non-linearity (S-box) add security to AES?

I'm trying to understand how AES guarentees security. One of the named points on the web is that AES uses a non-linear step (the SubBytes step). But how exactly does the Rijndael key schedule add ...
0answers
7 views

how do I implement identity-based signature scheme using PBC library [migrated]

i want to implement cha cheon id base signature scheme using pbc library....i'm very new to pbc library can any one help me.. and i'm very new to stack exchange please forgive me if I post anything ...
0answers
29 views

Trying to determine what encryption method was used [on hold]

I have a database I'm trying to decode. The database is an 1997 Microsoft Access database, and the program itself was written around 2001 in Visual C++. The database is used for decoding VIN numbers. ...
0answers
49 views

Message recovery using CBC

Take for example that alice has a message m that is 412 bits long, which she encrypts using AES-128 (which has a 128-bit blocksize) in CBC mode with a symmetric key k to produce ciphertext: c = Enc k ...
0answers
46 views

What followed findings of A. Lenstra et al. concerning shared factors of practical RSA moduli?

A. Lenstra et al. had a paper in 2012 "Ron was wrong, Whit is right", in which one reads: "What surprised us most is that many thousands of 1024-bit RSA moduli, including thousands that are contained ...
0answers
39 views

How to use a stream cipher to sign a message?

Are there known constructions which allow to sign a message M (let's say it will be sent as clear text) using a stream cipher C and a symmetric secret key K? So, we have M, C, K and we want to send ...
1answer
10 views

How to calculate $v_k(s)$ in Quadratic Arithmetic Program?

In the paper Pinocchio: Nearly Practical Verifiable Computation, there are some polynomials $v_k(x)$, $w_k(x)$ and $y_k(x)$ representing the structure of there circuit. However, as in the "concrete ...
1answer
48 views

Taking half of a X bits hash key as secure as using a X/2 bit hash function?

This question comes from a (nitpicking) comment by me in this SO question. I said that using the half of the output from a 256 bit hash function is worse than using a 128 bit hash function. My ...
0answers
29 views

David Chaum's anonymous credential

I am a newbie in cryptography (I know the basic RSA, AES stuffs) and am interested in anonymous authentication systems. Looks like David Chaum is the godly figure in the field. I see lots of people ...
1answer
39 views

Miller Rabin - Error probability of .5 a possibility?

I'm testing the property of Miller Rabin that the error probability is at most 1/4 when only a single base a is chosen and we iterate only one time. We are testing odd integers 90,000 to 100,000. ...
0answers
9 views

What's the perfect chain length : number of chains ratio for rainbow tables?

I'm building a SHA-1 rainbow table to crack basic passwords (i.e. up to 10 character, 0-9,a-z). But I can't seem to calculate that golden ratio that would give me the most coverage. Also is there ...
0answers
26 views

Implementing RSA in C# when Public Key is Known [migrated]

I'm trying to implement an RSA encryption function, but I'm new to cryptography. I know the public key and have data to encrypt, but I can't get the implementation correct in C#. I've tried using: ...
1answer
52 views

argon2 versus bcrypt/PBKDF2 password hashing security gain

I wonder if it can be approximated how much of a security margin the new argon2 hash, winner of the password hashing competition, can give over bcrypt or PBKDF2, for an attacker using large GPU ...
0answers
24 views

How to check the signature without the predetermined function in ECDSA from openssl?

I'm developing a client for a two-factor authentication in Qt/C++ under openSUSE 13.2, 64bit. I've got the FIDO U2F Security Key from yubico/fido. I'm using the classes from openssl, in particular ...
1answer
21 views

1answer
75 views

Probability of guessing random 128-bit AES key [closed]

Consider the following five events: Correctly guessing a random 128-bit AES key on the first try Winning a lottery with 1 million contestants Winning a lottery with 1 million contestants 5 times in ...
0answers
29 views

How to find the integer multiplicand from given two points?

I have two points on an elliptic curve $P(x_1,y_1)$ and $Q(x_2,y_2)$ and a scalar value $x$, where $P=x \cdot Q$. What is the best way that I could figure out the value of $x$? Given that I know all ...
1answer
38 views

Breaking a Modified Caesar Cipher

Does anyone know of an efficient way of breaking a modified Caesar cipher (where the key is a set of numbers (the amount of shift) that is repeated throughout the plaintext, e.g. {1,2,3,4,5}) via ...
0answers
25 views

Vigenere cipher [closed]

Ive been trying to figure out this vigenere cipher for a while now and not having much luck. cipher uses A-Z (0-25) and uses SPACE for 26. I'm trying to decode an encoded message but I don't have ...
2answers
63 views

Is there a way to do single key-pair asymmetric encryption?

All of the information on asymmetric encryption I can find uses key-exchanging to get a mutual symmetric key. What I am trying to do is encrypt a message with a public key and have it only readable ...
1answer
51 views

State of the art techniques for Anonymous Authentication?

What are the state of the art techniques for Anonymous Authentication? What are the most popular ones? The problem domain I am considering is with respect to different users accessing cloud content; ...
0answers
16 views

How can I encrypt a file with an ec public key? [migrated]

I have generated an EC public/private key pair using openssl with the following commands: ...
1answer
59 views

CTR DRBG dependent on request size?

I am trying to understand the CTR DRBG specification in NIST SP 800-90A. It seems slightly different to a pure stream cipher in that the key and counter are reset after each generate call using the ...
0answers
35 views

Show that using a PRF with a non-uniform key may result in non-uniform values

In a homework assignment we have to use a key derivation function like HKDF. Suppose $k$ is a non-uniform secret key sampled from the key space $\{0, 1\}^{256}$. In particular, $k$ is sampled ...
0answers
49 views

How to generate a bilinear group of prime order p for key generation

I asked the same question before. But an unregistered user i haven't any privilege to comment. So i am repeating my same question. I am trying to implement an IEEE Paper In Cryptography. I read many ...
0answers
14 views

How to generate a bilinear group of prime order p [duplicate]

I am trying to implement an IEEE Paper In Cryptography. I read many reference regarding an RSA key generation. But i am confused with above statement. Please someone explain me What it says with ...
0answers
37 views

Upper bound on r* on page 7 in the Scale Invariant Fully Homomorphic Encryption over the Integers paper

I was hoping to get some clarification on how the bound on r* was calculated (bottom of page #7). I'm trying to reproduce the results that have been shown, however I keep getting a slightly smaller ...
1answer
45 views

Which is better? Serialize and then encrypt or Encrypt and then Serialize

Let say in a simple Java program, Considering all the facts, like security and performance, Which is the best way to follow. I tried searching for a answer but proper answer is not out there.

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