# All Questions

154 views

Passwords hashed under Unix/Linux systems can use several hashing algorithms. ...
70 views

### Keyed-hash of a lot of small numbers

Let's say I have a list of several million numbers, with only 6-9 digits of secret information per number (this means that an attacker might efficiently guess the other digits). I have to store the ...
103 views

### Oracle DBMS_RANDOM algorithm?

Oracle DBMS offer builtin random number generator (pseudo to be accurate). DBMS_RANDOM is one of the available packages, it is however considered as insecure for cryptography. Do we happen to know the ...
24 views

### Why does a joint leakage MPC protocol not directly apply to a disjoint leakage requirement?

In the paper "Multiparty Computation Secure Against Continual Memory Leakage" on pg. 1239 the footnote at the bottom points out the difference between $joint$ leakage and $disjoint$ leakage. The ...
84 views

### /dev/random only needed for key generation / CPU pattern encryption

Consider the following scenarios: using OpenSSL to encrypt a file with Rijndael-256 using LUKS to encrypt a hard-drive that is used every day Exactly when is entropy from ...
104 views

### Distributed integer factorization?

I'm looking around for publicly published work on factorization of large numbers using distributed systems of any kind. So far I've come across the PDF "Mapreduce for integer factorization" by Javier ...
122 views

### Decryption honeypots

When performing a key search, I've always wondered how you reliably detect a successful decryption once you hit the right key. I assume that you have to analyze the data and look for patterns: words, ...
5k views

### Calculating RSA private exponent when given public exponent and the modulus factors using extended euclid

When given $p = 5, q = 11, N = 55$ and $e = 17$, I'm trying to compute the RSA private key $d$. I can calculate $\varphi(N) = 40$, but my lecturer then says to use the extended Euclidean algorithm to ...
177 views

### EC equivalent for RSA-OAEP

I have some questions regarding aforementioned subject: Is there a EC equivalent of RSA-OAEP key transport/encryption algorithm ? Is ECIES-KEM sufficient ?
285 views

### Coefficients in Shamir's Secret Sharing Scheme

Sorry if this is a stupid question, but: in Shamir's scheme, we construct a polynomial and make our secret $S$ the zero-th coefficient $a_0$. What, if anything, necessitates this - in other words, can ...
451 views

### FIPS 140-2 compliant algorithms in Enhanced RSA and AES Cryptographic Provider (Windows XP) [closed]

We have a native C++ application that supports Windows XP SP3. Recently we've decided to change our crypto algorithms to FIPS 140-2 compliant ones. We are planning to use the following algorithms in ...
22 views

### How to understand the Bilinear mapping with an example [duplicate]

An efficient bilinear map is given by $e$: $G_{1}$ × $G_{1}$ → $G_{T}$. How can i prove this equation with the help of an example.
213 views

### Encrypt and decrypt data accessible by multiple users within a team

I'm currently working on web services which allows to send and retrieve data. The data belong to a team. A team is composed of users. Each authenticated user can send and retrieve data to/from their ...
432 views

### How to Mathematically Prove the Bilinear Pairing Properties [closed]

I am currently working on Bilinear Pairing.To start my work i need to find the mathematically prove of three properties of bilinear pairing. Let $G_{1}$ and $G_{T}$be a cyclic multiplicative ...
2k views

### AES Algorithm processing time in Arduino vs Raspberry Pi

The Arduino employs an 8-bit ATmega series microcontroller whereas the Raspberry Pi is based around a 32-bit ARM processor, and the Arduino is typically clocked at between 8-16MHz and with 2-8kB of ...
208 views

### how do you calculate the private exponent in asymmetric key encryption [duplicate]

Here is an excellent paper on the math of asymmetric key encryption: http://www.mathaware.org/mam/06/Kaliski.pdf‎ See the example on Page 6. The public key = $55$ Primes used to calculate public ...
139 views

### One-Time-Pad with key-reuse: Faster way of decrypting?

I know there are already of few questions about this and I'm working with the advices that were given but I still doubt my approach is the fastest, so I'd really appreciate if you helped me find a ...
84 views

### What is the difference between homomorphic encryption and homomorphic signature? [closed]

I want to apply homomorphic signature instead of homomorphic encryption in Provable data possession. So I want to know about homomorphic signature and homomorphic encryption.
703 views

### Is there a feasible method by which NIST ECC curves over prime fields could be intentionally rigged?

The NIST elliptic curves P-192, P-224, P-256, P-384, and P-521, prescribed in FIPS 186-4 appendix D.1.2, are generated according to a well defined process, but using an arbitrary random-looking seed ...
413 views

### Where does the $\varphi(n)$ part of RSA come from?

$e d \equiv 1 \pmod{\varphi(n)}$ Where does the $\varphi(n)$ part come from? How did the inventors of RSA arrive at $\varphi(n)$?
245 views

### Is it possible to decrypt double-key crypted file knowing public key and a having one or more original files?

I have some encrypted files with double-key. I know public key and don't know private key. Can I obtain the private key (and decrypt all files) using two version of one file - crypted and decrypted? ...
79 views

### Possible to check if $a \in \mathrm{QR}_n$?

It is possible to check $a \in \mathrm{QR}_p \text{ iff } a^{(p-1)/2} \equiv 1\ (\bmod\ p)$ if $p$ is a prime. $n$ is a large RSA modulus. Is it also possible to check if $a \in \mathrm{QR}_n$ if the ...
333 views

### Why is the discrete logarithm problem assumed to be hard?

This might be a quite stupid question: since a naive brute force algorithm to solve the discrete logarithm problem will only take O(n) time for a group G with order ...
7k views

### Many time pad attack [duplicate]

I've already sent my correct solution to a homework exercise from Dan Boneh's Introduction to Cryptography class on Coursera: "Let us see what goes wrong when a stream cipher key is used more than ...
169 views

### Why use Needham-Schroeder if we have Diffie-Hellman?

If we want to establish secret symmetric key between two entities, why use Needham-Schroeder if we have Diffie-Hellman? With DH we don't need to have any trusted party, so what's the point of NS?
216 views

### Chance in cryptography

I was just thinking about my own chance and the way chance can defeat even the most advanced algorithm. My thought was : you can make a strong session id, but what if by chance, a hacker set this ...
100 views

### Time complexity to solve Discrete log problem

What is the time to complexity to solve Discrete log problem now in $Z_p$? Initially for $n$ bit prime $p$, it was $Exp(n^{1/3})$.
480 views

### One time pad key exchange

If two parties want to communicate with securely using OTP , how is the key ( that is lengthy as plain text) shared with other party for decryption ?
226 views

### Maximal-length LFSR with $n$ bits when the factorization of $2^n-1$ is unavailable?

There's a classical method to efficiently test if a LFSR with $n$ bits is maximal-length (or equivalently, if the feedback polynomial is primitive), when the factorization of $2^n-1$ is available. Do ...
306 views

### Methods of making ASIC/GPU resistant encryption?

Is there way to make encryption scheme ASIC and GPU resistant, besides using a lot of memory? And what is there ciphers or modes of use for such purpose? Including public keys algorithms maybe too, ...
83 views

### Is OCB with short MAC malleable?

At the beginning of OCB's white paper [pdf], OCB is compared to other modes, and non-malleability is one of the properties advertised. At the end of the paper, it is mentioned the MAC length can be ...
651 views

### Can I safely replace XOR with ADD in a stream cipher?

In a stream cipher, the bytes of the plaintext are usually XORed with the keystream to produce the ciphertext. Would there be anything wrong with adding the bytes instead (with overflow), if adding ...
284 views

### Difference between CBC-MAC and CMAC

According to Wikipedia, CMAC is based on a variation of CBC-MAC and fixes some security deficiencies in it. However, I could not find a simple and clear explanation of what the differences between ...
2k views

### ECDSA vs ECIES vs ECDH

Recently I started studying ECC and I just loved it. I want to transfer some big data (like 3KB), What is the best method, ECDSA, ECIES, or ECDH (and why)? I am confused, how should I choose between ...
448 views

### Do recent announcements about solving the DLP in $GF(2^{6120})$ apply to schemes proposed for cryptographic use?

A recent paper by Göloğlu, Granger, McGuire, and Zumbrägel: Solving a 6120-bit DLP on a Desktop Computer seems to "demonstrate a practical DLP break in the finite field of $2^{6120}$ elements, using ...
2k views

### Is Truecrypt's multiple/cascading encryption safe?

Is Truecrypt use of cascading encryption safe? Is it useful? Truecrypt is arguably one of the most popular and widely used encryption applications in use today, yet it seems to use a very ...
90 views

### 2PC Private Set Intersection Optimized for asymmetrically sized sets

I am researching some concepts of practical 2 party computation and was curious if anyone could point me to a research paper that is focused on private set intersection where one party has a very ...
78 views

### Is it possible to use structures other than finite fields?

I have some difficulties to understand why we are using finite fields in cryptography. Why do we use field? Why not ring or group? Is that really necessary that the field is finite? Why not real ...
165 views

### Cryptographically secure product keys

I am looking for a scheme to generate and validate cryptographically secure product keys. My requirements are: Unforgeable. It must be impossible (or at least very hard) for users to forge a product ...
270 views

### If G is a secure PRG and G' is a function of G, is G' secure?

For example: for secure PRG G if I have a G' s.t. G'(k) = G(k)||0, is ...
254 views

### How is the AEScrypt password related to the underlying AES key

AES uses a key that is at most 256 bit. I assume AESCrypt uses AES. When a file is encrypted with AEScrypt, there is no limit to the length of the password. What is the relation between the ...
292 views

### Are the SHA family hash outputs practically random?

Say I hashed the output from a random number generator (with nonce), would the resulting SHA256 hash be as random as the inputted number? And If I used the first 5 hex characters, and then used the ...
295 views

### Brute force a ciphered message? [closed]

I wrote my own cipher to encrypt messages. I would like to test a sample ciphered message to see how strong it is. Are there any tools for such task either in Windows or Linux ?
447 views

### ECC - Point Addition/Point Multiplication

So I have a very beginner-esque knowledge of ECDSA and I'm trying to write something in python to take a private key and output the public key (Basically from what I understand just trying to do the ...
121 views

### Recovery of RC4 key when S-box 0 stage or 1st stage known

I've been exploring around, trying to understand if such thing is even possible. I have some RC4 ciphertext which I know it's plaintext and I would like to extract the key just from cipher and ...
257 views

### Why do I need to add the original salt to each hash iteration of a password?

I understand it is important to hash passwords over multiple iterations to make things harder for an attacker. I have read numerous times that when processing these iterations, it is critical to hash ...
168 views

### RSA key length choice for TLS when confidentiality not important?

I've a couple of questions about this, the scenario is embedding a key pair in a hardware device which will speak with other hardware devices over tls. computing resources are an issue so i want to ...
134 views

### Why does DSS have such formulas?

I've learnt the formulas needed for the DSA (http://en.wikipedia.org/wiki/Digital_Signature_Algorithm). But most importantly, I don't quite understand what represents those formulas and why they are ...
I was unable to solve the multiplication table given in the book for $\mathrm{GF}(2^2)$.However, I have managed to solve the addition table. Acoording to the Book multiplication is the AND operation, ...
Considering a CPA-secure version of RSA where the ciphertext is just a rundom element from $Z^*_N$. Does that meet the anonymity requirement in which an cpa adversary cannot distinguish between a ...