# All Questions

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### Research Path For Searchable Encryption

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 ...
28 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 ...
24 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 ...
47 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.
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### Feistel network output if round function is the identity function

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 ...
14 views

### Secure(verifiable, delegated, outsourced) computation

Can we think "secure (verifiable, delegated, outsourced, 2-parties and multi-parties) computation" as a same single concept, or should we consider these secure protocols as different concepts? If ...
16 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?
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### 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 ...
19 views

### Cryptanalysis of Non-Binary LFSR

Here we have a class describing a LFSR working over the integers modulo n. ...
36 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?
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### 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 ...
23 views

### Mifare Classic and crypto1 algorithm

Mifare's Crypto1 algorithm uses a 48-bit LFSR. What does the 48-bit LFSR do exactly ?
16 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, ...
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### 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).
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### Decrypt with only the cipher file and the key?

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 ...
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 ...
17 views

### columnar transpostion

What is the plaintext of this columnar transposition cipher or is there any related doc- EPAHR ELNFO CPOIO ASROS MWIWA SOTAV TIOES INDED DXTAT YTNTU OMEPC ASFCR LTORN MOGRA SAORO SLLAH AMGAB OGTEW ...
48 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 ...
28 views

### Is salt bring more security for digital signature!

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?
33 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 ...
24 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.
75 views

### Real life systems that use concepts of crypto computing

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 ...
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### 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. ...
35 views

### Are all binary-additive stream ciphers reciprocal?

I'm writing a thesis focused on Maurer's provably-secure stream cipher. Long story short, this cipher works by expanding a short key into a long keystream and then XORring this keystream with the ...
62 views

### What is the difference between order of base point and curve order in EC?

When I was read about the elliptic curve cryptography I found some definition about domain parameter of elliptic curve like the follow. But I did not understand something $p$: prime number. $a, b$: ...
99 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 ...
19 views

### Is there a Javascript and Java implementation of a good CSPRNG [on hold]

I need to use a cryptographically secure pseudo random number generator in my client running Javascript and in my server running Java. Is there a well-known implementation of a good CSPRNG in both ...
36 views

### Proving correctness of a decryption of a homomorphically summed ciphertext?

I would like to take some additively homomorphic cryptosystem - don't care much which one for now - and encrypt a series of numbers with it. I would then like to (in public) take these numbers, add ...
35 views

### Difference between signing with SHA256 vs. signing with RSA-SHA256 [on hold]

I play with digital signatures using node.js (server side JavaScript, built on Google's V8 JS engine). There is a "crypto" module included. For test purpose, I created a digital signature of some XML ...
40 views

### Cryptographic Operations and Security

sign((M’, TAlice, sign(( encrypt(( encrypt(M, KpbBob), M’), K), TBob), KsBob)), KsAlice) Can you tell me six security-related facts ...
62 views

### Availability of a simple limited PRNG algorithm

I am in need of a really simple limited PRNG, that either exists or can easily be created in virtually any language on any platform. It takes only the initial seed, and is only expected to generate a ...
53 views

### Is there an “additive” proof-of-work?

I'm trying to find a proof-of-work algorithm with the following properties: If A(1) is a proof of work with Difficulty(A(1))=n (requires n basic operations on average), then one can find a proof of ...
45 views

### Should I study advanced abstract algebra and more than elementary number theory to pursue a career in cryptography?

Do I need to study advanced abstract algebra and more than elementary number theory in order to pursue a career in cryptography ? I've already taken a course in abstract algebra, but I'm wondering ...
64 views

### To prove $r \cdot f_1 +f_2 \cdot (s+1)$ is secure

We define the polynomials $r, f_1,f_2,s \in R[x]$. Where $r$ is a random degree 1 polynomial and $s$ is a random polynomial such that: $degree(s)=degree(f_1)=degree(f_2)$, let $R$ be $\mathbb{Z}_p$ ...
67 views

### AES - Encrypting multiple blocks of files

On my site, users can download files which are stored on public hosting, so I need to encrypt them. A downloaded file is divided into blocks of 1 kB and I want encrypt them individually, using the ...
34 views

### homomorphic paillier cryptosystem vs Elliptic curve cryptosystem [on hold]

what are the pros and cons of homomorphic paillier cryptosystem compare to Elliptic curve cryptosystem??