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Check correctness of data using only publicly known variables and a server response

A smart contract (a publicly known program) needs to check if the data D is correct (belongs to some fixed set). It is by definition correct if our trusted server checks it and decides it's correct. ...
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31 views

Rules Governing Duplicate, Repeated Characters While Encrypting Plaintext to Ciphertext

What is the general rule if there is one that allows the encryption of a plaintext message to ciphertext message to be able to mask duplicate or repeated letters in the plaintext. This is an arbitrary ...
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66 views

How is it that homomorphic encryption can encrypt program code and run it without decryption?

In my journey of interest in the world of homomorphic encryption has led me to a concept floating around the internet where they describe homomorphic encryption being used with "mobile agents&...
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49 views

Is the "grain" in this converted image indicative of Steganography?

I'm checking an image in every way I can for steganography. I've checked the file signature, compared it to it's original source and extracted the pixels, many methods but nothing's coming up. ...
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134 views

Randomness Testing of Block Ciphers with 256-bit Block/ Key length

NIST explained the process of "Randomness Testing of the AES Candidate Algorithms" in the document. The document explains the generation of 9 datasets for AES candidates with 128-bit block ...
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57 views

Bitcoin ECDSA signature

I am trying to use the ecdsaSign function in ecdsa.c of https://github.com/kvhnuke/Ethereum-Arduino/tree/master/Ethereum-Arduino/libs which is based on the files in the repo https://github.com/...
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1answer
94 views

Exponentiation Problem of G2 in MNT curve

I made a simple python program in the Charm framework (https://github.com/JHUISI/charm): ...
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69 views

Security of CCM using 8 byte MAC within TLS

In the Dutch "IT Security Guidelines for Transport Layer Security (TLS)" the ciphersuites using AES-128-CCM_8 (i.e. CCM with a 64 bit authentication tag) are considered "insufficient&...
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143 views

Probability of collision when we use a particular part of sha 256 hashed value

So I was supposed to use hash some co-ordinates and I was supposed to use k 3-wise independent hash functions in order for the mathematical explanations behind that algorithm to be hold. But after ...
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330 views

How do you verify that an address is related to a private key

This is my first post. My interest for cryptography is exclusively motivated by cryptocurrencies. My question is: If I generate some keys, how do I actually verify that the address is indeed ...
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62 views

Can I use zero-knowledge proofs on pre-image of symmetric encryption?

Let $e_x$ be a symmetric encryption function in regards to key $x$. Let $y_1 = e_1(x_1), y_2 = e_2(x_2)$. My goal is to prove that: $$x_1 = x_2$$ Is there a way of proving this using ZKP? I can't seem ...
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89 views

Is there a relation between the private keys of secp256k1 public keys of opposite parities?

From observation, 32 bit public key values of opposite parities are either both valid, or both invalid. ...
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130 views

"16-bit DES encryption algorithm"

I need to use encryption software from PSpice for my SPICE model. In a user guide on page 71 they claim to use a "16-bit DES encryption algorithm". According to the wiki DES is using a 64-...
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60 views

is it safe to do public key to public key derivation with Ed25519?

Deriving a public key from a public key in Ed25519 is possible, some algorithms are available. My question is why there are so few implementations compared to secp256k1 for example. The extra checks ...
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91 views

Client-Side Encryption for a small app

I'm designing a small personal journal web application for my wife. I'm a crypto newb, but I want her to feel secure knowing only she will have access to her journal entries. I am thinking of the ...
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31 views

Where can I find references to the theory behind PBC library?

I don't know if this is the right place to ask this type of question. Anyway, I'm using PBC library for a project, but I'm a very newbie for what concerns pairing based cryptography. Then I ask some ...
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197 views

Fast Extended Euclidean Algorithm in Harley's elliptic curves point counting method

Could you help me with Harley's norm computation algorithm that is based on the Fast Extended Euclidean Algorithm that was suggested by Harley in an email to NMBRTHRY list in 2002 and that described ...
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42 views

Binomial distribution sampling - concrete example

Can anyone give me an explicit example of how one can samples from the binomial distribution defined in NewHope's paper? What is the difference of sampling from rounded Gaussian in practice?
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45 views

How to justify the lightweight symmetric PRESENT encryption algorithm is more secure?

My domain is VLSI design, currently, I'm working on PRESENT Lightweight cryptographic algorithm. I want to know how to improve the security of the algorithm rather than increasing bit size? Is there ...
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39 views

Digital Signature or MAC Yielding Non-Binary Verification Predicate

Is there a digital signature or MAC scheme in which, the verification algorithm returns not $\{\text{Valid},\text{Invalid}\}$, but a discrete (finite or infinite) set of result such as $\{\text{Valid-...
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62 views

Elliptic curve group inverse addition in OpenSSL

I am using group P-256 on OpenSSL with C++. My understanding was that, if you have a point $xP$ and then calculate (xP)^(-1) with EC_POINT_invert(group, xP_inv, ctx), then when I calculate: xP + (xP)^(...
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73 views

What is the best deterministic authenticated encryption algorithm to date?

We have a main database where certain properties are PII and want to setup a read-only replica so other parts of the business can able to access (e.g. analytics) We'd like those PII properties to be ...
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61 views

Modulo hashing scheme

Let's consider hashing of odd 256-bit number $L$ with 256-bit odd key $K$: $z = (2^{256}-L) \cdot K \bmod 2^{256}$ $z$ is the hashed number. If $K$ is selected randomly is it secure to hashing ...
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56 views

Any gotchas when deriving a symmetric key from two seeds?

Consider a connection protocol where, after jumping through several other hoops, Alice and Bob know each others' public keys; and they now want to do a RSA-handshake-kind-of-thing to come up with a ...
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1answer
70 views

How to Update Non-Membership Witness upon deletion in RSA Dynamic Universal Accumulator

The Universal Accumulator paper mentions the following for updating non-membership witness upon member deletion. Choose $r$ such that $a\hat x − rx ∈ Z$$2^l$ What is Z$2^l$ and how can we ...
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38 views

How would I get started in auditing and finding vulnerabilities in encryption algorithms?

I know, it sounds dumb. Very dumb in fact. But regardless, I want to actually begin doing security research on cryptographic algorithms (SHA, RSA, ECDSA, etc.). I would prefer that this question be ...
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77 views

Semantic Security in Formal Security Proofs

I have a trivial question, and I hope someone can help me. I am reading several papers on formal security proofs based on the indistinguishably game. Specifically, the adversary is challenged in an ...
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60 views

Same private key for signing and decryption

I am designing a service which identifies records with public keys. All other fields are encrypted with that public key and protected by a HMAC. For authentication, I am thinking about signing ...
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26 views

How big could be nothing-up-my-sleeve numbers to initialize key schedule?

Is it fine if algoritm will have $32$ 128-bit numbers that will be nothing-up-my-sleeve numbers to initialize key schedule? As I know from wikipedia the Hasty Pudding Cipher was criticized for its ...
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57 views

Small (code-size) hash functions

I am trying to implement a small encryption tool in as little code as possible as a learning exercise, and currently have managed to get everything to depend only on a HMAC construct. However, most ...
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86 views

Which cryptographic attacks can AES 128-bit withstand?

Most of the articles and forums are stating that the Brute Force attack can test the strength of an encryption algorithm. However, I am looking for those attacks that AES can withstand for the testing ...
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98 views

ROLLO : security bits parameters

In ROLLO -Rank-Ouroboros, LAKE & LOCKER p.20, it says that "Notice that for 128 security bits parameters, the practical security is rather higher than 128 at about 170 bits." How Can I ...
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32 views

How Should Form Input be Encrypted for sending to a Server?

I apologise if this question is a duplicate. I couldn't find any similar questions. I am writing a web app that consists of a series of drop-down style question menus. These generate more drop-downs ...
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25 views

Authenticating and encrypting data for an automated system

I wish to distribute a file from A to an automated system B. The requirements are: Contents are encrypted Contents are tamper proof Contents origin is verified To do this I have devised the ...
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38 views

Is $f_N$ in this hash function is Matyas-Meyer-Oseas scheme?

I propose a hash function as following: H is an Merkle-Damgard hash function with a compression function $f: \{0,1\}^{3n} \to \{0, 1\}^{2n}$. Output function $f_N: \{0,1\}^{3n} \to \{0, 1\}^n$. M is ...
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52 views

Security implication of concatenating two hashes using different algorithms

Background Hashing files is an expensive thing for CPU. I am tasked to write a secure digital signature scheme. For that, I decided to check the integrity of files using Hash/Digest. To be more secure,...
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34 views

How to prove properties of pre-image of random oracle in zero-knowledge proof?

A signature Sig is given as input to random oracle H, such that y = H(Sig) and Sig should be hidden from the verifier. How to prove in zero-knowledge to the verifier that y is the correct output from ...
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59 views

RNG randomization strength for PRF seed

Consider a use case that requires the creation of multiple asymmetric key pairs. There are two options for generating random seeds for a PRF: Use a software based RNG and generate a new seed for each ...
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1answer
127 views

Prior art: SSH key authn over TLS?

I’m developing an application that runs over TLS. In addition to password-based authentication we’d like to be able to use SSH keys. Is there any prior art in using SSH keys for authentication over ...
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84 views

RSA How many value for d

How many value can have a private key with this format? p,q,d = (19, 41, d) where 1< d <18x40? I want know how to calculate that.
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39 views

How to estimate the computation overhead of ECDSA?

I am using ECDSA as a digital signature scheme. Using Charm, I got the timing for the multiplication, exponentiation, and pairing operations; they take 0.005, 9, and 4.4 ms respectively. I want to ...
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26 views

Could someone please explain the implementation of public-private key encryption for storing passwords?

As someone new to cryptography,I have a question about how logins work on websites. I understand mathematically how asymmetric encryption works and how https web requests work to securely send ...
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83 views

RNG to hide some bits

Suppose I have a sequence of bits of length M. I need to hide N out of M bits (hiding means forcing them to be 0) using RNG with a key. How I can relate the output of RNG to the number and positions ...
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58 views

Which public-key cryptosystems are used the most?

Does anybody know if there is some kind of measure on how often public-key cryptosystems like El Gamal, RSA,... are implemented. Which ones are most common?
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51 views

Attack on Many Time Pad

I have 7 ciphertexts that have been XORed with the same key. I'm writing a program to figure out what the plaintexts are and possibly maybe recover the key. I have managed to convert the HEX ...
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87 views

Authentication using a nonce

For an authentication problem imagine the following scenario with two devices: 1 server 1 client. The client starts a conversation with the server and sends him his public key. All public keys in ...
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60 views

How to design number of rounds in my cipher?

I have specific cipher which is built from permutations. It has or should has few rounds. If we do 2 rounds it is like 2 permutation composition. 3 rounds are like composition of 3 permutations and so ...
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75 views

Why cant we use AES to hash a password, instead of a hash function?

AES needs a key in order to work, hashing-algorithms do not. Suppose we have a fixed key for AES, why don't we simply hash our keys with that? As with hash functions, AES has arbitrary input size, ...
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138 views

Secretbox- algorithm Poly1305 and cipher Xsalsa20

I use Rclone, which uses Secretbox to authenticate and encrypt data. Secretbox uses the Poly1305 authentication algorithm and the Xsalsa20 symmetric flow cipher. This whole process takes some time (...
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130 views

How to Derive a Child RSA Key Pair from an Existing RSA Key Pair?

I want to understand how, using standard tools like openssl (or similar), to derive a child RSA key pair from an existing RSA key pair. Additionally I would like the derived key to contain a ...

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