# All Questions

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### Translation of Schorr Ring Signature to ECSchnorr Ring Signature

I have to write an EC version of Schnorr Ring Signature Scheme. I've already wrote regular ECSchnorr Signature Scheme using this (page 128). I've found a scheme of Schnorr Ring Signature Scheme (page ...
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### What are the negative consequences for choosing 8 S-boxes for DES vs 1 S-box for AES?

DES has 8 different S-boxes, and AES has only 1. What are the negative consequences of such choices?
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### NTRUSign Hashing

I have some trouble understanding the inner workings of NTRUSign. So what I have understood so far is, that when Alice wants to sign a message she does the following steps Convert Alice's message ...
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### Is it possible to re-generate ECPublic key from raw private key and curve params?

As per my understanding, in Elliptical curve cryptography, the EC PrivateKey is nothing but a bigInteger value. If you know the curve specs and you have this private BigInteger value (which I am ...
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### How to test the speed of an Authenticated Encryption algorithm?

I am trying to implement Authenticated Encryption algorithms using CUDA. Most of Authenticated Encryption algorithms have short message length like 64, 254..., 4094 (Byte). these message lengths ...
52 views

### what is the fastest and efficient method to perform modular multiplication?

I'm working on a code that needs to perform modular multiplication of big numbers several times. Since the operation takes place several times, using division to find the remainder is very expensive. ...
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### How to calculate Private Key in RSA using Extended Euclidean Algorithm [duplicate]

I have googled for about 2 hours now and still haven't found an explanation. The wiki article just makes me more confused and so has every other similar question I've found on StackExchange. Here's an ...
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### Can knowing part of what was used to generate an md5 hash make it vulnerable? [duplicate]

Say I am able to ask a black box MD5 generator to generate 1,000,000 hashes given input $STRING$ Where $STRING$ is an arbitrary ...
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### (Looking for reference) Variants of Diffie-Hellman

Sorry for asking a non-pure-crypto question but I think that crypto.SE might be the right place to find the right people to answer this: I remember having seen a few years ago, online and in HTML ...
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### What type of encryption scheme can prevent cheating in this coin flip protocol? [duplicate]

Consider the following protocol for two parties to flip a fair coin: Trusted party $T$ publishes her public key $p_k$ A chooses a random bit $b_A$, encrypts it under $p_k$, and announces the ...
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### gpg 2048R - why encryption data length is different if text data 36 bytes

We are using gpg2 and base64 commands with 2048R algorithm Input: encrypted 36 bytes input text data with fixed length(36 bytes) current problem: if I run gpg command continuously, some times ...
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### trusted platform module prototype

I have a Java card, which I like to learn more about by installing my own TPM on it. One, which I can kind of "kick the tires", install root keys, send different command to, and ... without fear of ...
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### Symmetrical Block Encryption with Synchronised Remote Key Change

I'm considering a theoretical design of a walkie talkie, with strong encryption. My current idea is to use symmetrical block encryption, but with the key changing at regular time intervals without a ...
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### Unbreakable encryption [duplicate]

I am a newbie, I know that I must be wrong, but I need a good explanation. How is it possible to break a cryptographic algorithm created by me, when only I know the algorithm and the key for ...
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### Reversible hash function

I met the following 'reversible hash' function applied on a data $d$ consisting of $d_1, \ldots, d_n$ words: $h_0(d) = 0, h_i(d) = c ∗ (d_i + h_{i−1}(d))$, for $0 < i \leq n$. $c$ is a small, odd ...
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### How to check if a function is significant or not?

f(n) = 1 / ( log n ) ^ 1/2 I know that this function is not negligible because it will never converge to zero even for large values of n. Now my question is, how ...
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### 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 ...
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### How does ABE decryption works? [duplicate]

I am trying to understand how Attribute Base Encryption (ABE) works. So, after downloading libfenc library from here, I built the source code on Ubuntu 12.04 without any error. Afterward, I tried to ...
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### 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 ...
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### Does CPA attack assumption requires the oracle to have the key?

In CPA model, we assume Eve has access to an oracle who has the correct key and Eve can send query to the oracle to encrypt in CPA the data. Assume this encryption algorithm is a plain ECB mode AES ...
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### How do we measure number of possible encryptions in One Time Pad [duplicate]

trying to brute force a specific length of ciphered pad, how do we measure the total number of possible encryptions in One Time Pad
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### Advantages of the general digraph trust model over the strict hierarchical model

Are there any advantages of using reverse certificates and the general digraph trust model over the strict hierarchical trust model as described here: In the digraph model each CA can generate ...
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### Strength of a cryptography algorithm [duplicate]

I'm just read this article from Atmel corporation in comparing RSA with ECC cryptography algorithms. First of all please read these two paragraphs quoted from the article: P1: Strength of an ...
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### Why we use operating modes in cryptography? [duplicate]

Why we use operating modes (CBC , . . ) in cryptography? i mean what is the essential of use it ?
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### What is the DK function when generating an AES key for Kerberos 5?

I'm trying to understand RFC3962. So far I understood everything, except for the last part: generating the derived key from the PBKDF2 output. To generate an encryption key from a pass phrase and ...
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### How do I check if the secret key polynomial of the ATV-FHE (NTRU based) scheme is invertible?

I want to implement the ATV-FHE scheme as described here https://eprint.iacr.org/2014/039.pdf. To generate the secret key polynomial I compute f = 2*u + 1 , with scheme parameters chosen such that ...
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### Encrypted vs unencrypted digital signatures [duplicate]

Is there a difference in terms of security between An encrypted stream of bits obtained by encrypting a plaintext concatenated with it's signature $C = E_k(plaintext||\sigma)$ where $E$ is a ...
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### How to sign an elliptic curve point using an ECC signature scheme?

In Schnorr based ECC signature scheme, a message $M$ is signed with the private key $\mathit{sk}$ as $$s=\mathit{sk}\cdot h(M,R)+k$$ where $R=k\cdot P$ and $P$ is a base point. If $M$ is a point ...
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### With AES-GCM, can the encrypted and non-encrypted parts be hashed separately? [duplicate]

The hash function in AES-GCM takes encrypted and unencrypted parts. Can the two parts be provided in either order? I'm wondering whether there is any fun with $GF(2^{128})$ that can be done to ...
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### IV re-use for Salsa20 [duplicate]

Are their any specific requirements for the IV when using Salsa20? Is it for example allowed to re-use the same IV when encrypting with the same session key? Should the IV be random? etc I tried to ...
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### what is the difference between one way function and hard core predicate?

Does anyone know what the difference between a one way function is and a hard core predicate? Are they related to each other or different?
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### Difference between SHA1 and SHA1HMAC? [duplicate]

Can anyone let me know the difference between SHA1 and SHA1HMAC algo?
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### Which parameters of the ATV-FHE scheme should be kept private?

I try to implement the ATV-FHE scheme as it is described in section 2 of this paper. I also read this paper that says how parameters should be chosen. Are there some parameters that must be kept ...
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### In FHE over integers is each bit of the cyphertext encrypted under the new key?

In the paper Fully Homomorphic Encryption over the Integers, a method is shown for doing homomorphic encryption using only integers. The basic idea is that a bit m is encoded as a large integer c. ...
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### How to decrypt RSA cipher text? [closed]

How can I decrypt an RSA cipher text in which I am only provided with a public key and the cipher text. The person who encrypted it made a mistake in taking the exponent.
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### Intermediate values for testing Blowfish

I am trying to implement the Blowfish algorithm in VHDL. To debug my code, I need the intermediate values of s-box and P vectors after each iteration. Where can I find this data set? p.s :- I know ...
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### SHA-256 Hash over multiple SHA-256 Hashes

I am trying to implement a checksum over multiple files. We can assume, that i have a package containing N files. I want to identify such a package uniquely by following calculation: SHA256-Hash ...
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### What is the bound for the probability distribution for ATV-FHE scheme?

I try to implement the ATV-FHE scheme as described in this paper https://eprint.iacr.org/2014/039.pdf. How do I choose the bound for the probability distribution chi? How do I choose standard ...
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### How to choose moduli ladder for ATV-FHE scheme?

I try to implement the ATV-FHE scheme as mentioned in section 2 in this paper https://eprint.iacr.org/2014/039.pdf. In this paper, authors say this "For example, given a 256-bit prime q ..." in ...
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### Existence of a random function under constraints

Let $F_1$ and $F_2$ be two random functions taking as input $N$ bits and returning $N$ bits. Let $C_1$ and $C_2$ two constants of $N$ bits. Is there a random function $P$ taking as input $2N$ bits and ...
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### How to toggle a bit homomorphically ?

Suppose I want to use LTV scheme from this paper https://eprint.iacr.org/2013/094.pdf to compute homomorphically a function. But the multiplication operation is more expensive than the additive one. ...
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### Symmetric encryption with compression for MySQL DB data

I would like to compress data before encrypting and storing it in a MySQL DB to reduce especially bandwith requirements (compression reduces bandwith by 70-80%). At present, all is handled by a ...
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### Having doubt in Rijndael Algorithm- coding for decryption

I am doing a project on the Rijndael Algorithm. I have already written the encryption code which produces the correct output. Now I want to implement decryption as well. I'm doing using VHDL, ...
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### File encryption using per-user-encrypted shared key

So I'm looking to encrypt files using AES CTR, using a shared key which would be accessed via a per-user password. My two main concerns are: - making sure that the algorithms in use are appropriate ...
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### Multiplication in GF(2^8)

I am trying to multiply 13 (sub 16) and 11 (sub 16) in $GF(2^8)$. I am given the following irreducible polynomial: P(x) = x^8 + x^4 + x^3 + x +1 Could someone explain to me how to express the ...
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### Need help implementing key management scheme

Scheme has following requirements Client application should perform encryption/decryption using component 1, component 2 and ZPK (zone PIN key. Client should get this key from host in encrypted ...
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### Understanding RSA [duplicate]

I'm reading RSA in Cryptography Course. There is portion of RSA that's confusing me. In Handbook of Applied Cryptography its written Represent the message $M$ as ...
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### Detecting Software Changes - Verifying untampered code

This question assumes an environment devoid of any internet connections, the software in questions operates in a non-connected environment on a single machine. I have a piece of software that may be ...
I am doing a paper on textbook RSA (this is for high school btw) and in my example I need two very large primes, but I want my $e = 3$. Is there a short way to calculate the values of $p$ and $q$ ...