0
votes
0answers
10 views

Problem when programming Schnorr signature

I have some questions about Schnorr signature implementation. I am trying to implement it in C++. I chose private signing key x and public verification key y = g^x. I have a message M, random number ...
1
vote
0answers
6 views

How are keys stored in a .keystore file or in a .jks file?

I would like to know what is the structure of the keys stored inside a .keystore or a .jks file? by structure I mean are the keys stored in key value pairs? how are the passwords for several keys ...
0
votes
0answers
11 views

How can I convert an image into a long hexadecimal code and vice-versa?

Title. Characters to fill required 30 characters minimum.
0
votes
3answers
47 views

Public key decryption mathematical analogy

To clarify, I'm talking about digital-signatures, not public key encryption. When I encrypt something with a private key, then it should be decryptable with a public key, as I've understood how ...
3
votes
0answers
36 views

Applying machine learning algorithms to homomorphic encrypted data

I have a basic understanding of encryption and I got back to the topic because of an interesting site that encrypts financial data using homomorphic encryption (HE) and I would be happy for any input ...
-1
votes
0answers
32 views

what are the kind of mathematical proofs that i need to be familiarized with to understand (or do) cryptography? [on hold]

I know reductions are highly used to show that encryption schemes are secure under certain conditions, but i don´t know what other math proofs are needed. PD: English is not my native language so ...
3
votes
1answer
27 views

Using master password to encrypt and decrypt user credentials

I need a way to store third party credentials, and I want to avoid storing passwords in plain text. I can't use a hash because I will need to be able to get the raw password to log in to the third ...
1
vote
0answers
25 views

How would low-precision Gaussian sampling impact the security of BLISS?

For digital signature, I implemented BLISS in my cryptographic suite, and wrote the Gaussian sampler based on Lattice Signatures and Bimodal Gaussians. But unlike the reference implementation and ...
-1
votes
0answers
10 views

ocf-linux, Splitting large buffers into chunks < MAX_DATA_LEN [migrated]

I am using ocf-linux in an openwrt application and have run into OCF CRYPTO_MAX_DATA_LEN (64K-1) and E2BIG errors in CRYPTO_AES_CBC mode. As a consequence, I need to split the input buffer into ...
1
vote
3answers
45 views

Is there a PRNG algorithm that allows to switch between states directly, not calling next()?

Basically I need a function with the following interface: getRandomBytes(uint128 seed, uint64 state, uint16 byteCount) Consecutive calls with the same seed and ...
4
votes
2answers
69 views

Is it ever safe to use encryption with compression?

In the wake of compression-based side-channel attacks like CRIME and BREACH, are there any safe ways to combine compression and encryption? The JWE Specification was finalised almost 2 years after ...
0
votes
0answers
15 views

Is there any functional encryption scheme whose key generation circuit is in NC1?

To my best of knowledge, I have kown there exists randomized encoding scheme whose encoding circuit is in $NC^1$, fully homomorphic encryption scheme whose decryption circuit is in $NC^1$, and ...
3
votes
0answers
29 views

RAR brute force cracking speed

I have been playing around with cRARk and was astonished by the low speed. On a 2015 high-end GPU (GeForce 980 ti), it took roughly 4h 50min to test all passwords composed of an 8-character prefix and ...
0
votes
0answers
36 views

Independence of answers to queries sent to a random oracle

Assume we have an algorithm which asks random oracle $\mathcal{O}$ $Q$ queries $u_1, \ldots, u_Q$. All queries are unique, $u_i \neq u_j$ for $i \neq j$. Queries $u_i$ are random variables, too. What ...
1
vote
1answer
105 views

Do I need to prove this?

I am using ABE scheme that has already proven under BDHE assumption. Here is the scheme https://eprint.iacr.org/2008/290.pdf In the key generation algorithm, I want to tie the user secret key ...
2
votes
1answer
32 views

Why is it so hard to make longer hashes?

I was reading this answer about why there is no such thing as a SHA-1024 hash: SHA-2 was built with state and word sizes to meet the security requirements on commodity computers (x86 and Alpha), ...
0
votes
0answers
31 views

How do Raptor (Fountain codes) encoding and decoding work? [on hold]

As described in this article, a Raptor code is a fountain code that encodes a message of $k$ symbols into a limitless sequence of encoding symbols, such that knowledge of any $k$ or more encoding ...
1
vote
1answer
27 views

Secure logical AND using Ishai-Sahai-Wagner Scheme

I want to try to implement a secure AND the way it was described here: https://eprint.iacr.org/2010/441.pdf It says that there are two bits a and b and that they have been split into d+1 shares. How ...
5
votes
1answer
101 views

RSA: revealing the modulus factorization by choosing a bad message

I started reading the book Cryptanalysis of RSA and its variants by M. Jason Hinek and I stumbled upon a phrase that intrigued me: plaintext messages that are relatively prime to the modulus (i....
1
vote
1answer
60 views

Given $ g^s, g^y , g^r, g^t, g^{st-rs}, g^{(yr+d)/t}$ , is it hard to distinguish $e(g,g)^{syr}$ from a random value?

Where $g$ is a group element in bilinear group $G$, $e(g,g)∈GT$ and $s, y, r, t, d$ are randomly chosen. I understand it is very similar to the conventional DBDH problem, but $g^t, g^{st-rs}, g^{(yr+...
2
votes
1answer
37 views

Given $g^a, Y$, is it hard to distinguish $e(g,g)^{ab}$ from a random value?

where $g$ is a group element in bilinear group $G$ $Y = M.e(g,g)^{ab}$ $M$ is a message Does anyone know the answer or suggest some material for reference? Many Thanks
2
votes
1answer
33 views

Using the Unix epoch as nonce

Since a nonce must be unique and that time only goes forward, is it safe to use the Unix epoch as nonce ? My use case is be AES w/ GCM which recommends a nonce length of 12B. Current Unix time can be ...
0
votes
1answer
30 views

How secure is encrypting with self-hash [duplicate]

I don't have much knowledge about cryptography beyond using libraries for it. So just wanted to understand if the following two cases differ sufficiently in security or is it just psychological: Say ...
0
votes
0answers
35 views

Is it possible to turn an image (e.g. a photo) into a cryptographic hash? [on hold]

I am looking for a way to turn an image (e.g. a photo captured on a phone) into a cryptographic hash (e.g. SHA256). Is this possible? If so, how?
1
vote
1answer
47 views

Is security against semi honest adversary inheritable?

I have a two party protocol, let's call it $M$. At some point, there are $k$ steps, each one involving an oblivious transfer protocol, which is known to be secure against semi honest adversaries. ...
0
votes
1answer
36 views

Decomposing an ideal in intersections

Let $R$ be an ring, and let $(a),(b)$ be the ideals generated by $a,b\in R^\times$ respectively. Let $c=a\cdot b$ and $(c)$ the ideal generated by $c$. I am supposing that, given $c$, it is ...
5
votes
0answers
52 views

Using a single Ed25519 key for encryption and signature

The libsodium documentation contains a function crypto_sign_ed25519_pk_to_curve25519 that converts an Ed25519 key into a Curve25519 one, so it can be used for both ...
1
vote
0answers
19 views

How long is the tag T in AES-GCM(Or: Can implementations freely choose t = len(T)?) [duplicate]

I've started to learn about GCM. In the paper I read on page 4 there is the equation: $$ T = \text{MSB}_t(\text{GHASH}(H, A, C) \oplus E(K, Y_0)) $$ It's clear to me that the function $\text{MSB}_t(S)...
2
votes
1answer
50 views

When is AES chosen instead of a stream Cipher (e.g., RC4) during an SSL connection?

During an SSL handshake, the browser sends a list of cipher suites to the server, from which the server selects one option. For data encryption, two of the several possibilities for the ciphers in ...
2
votes
2answers
31 views

Homomorphic Encryption operation for regression

I must be missing something, and I am sorry if this is a novice question... I have seen in places (eg. https://crypto.stanford.edu/~dwu4/talks/SecurityLunch0214.pdf page 13) that linear regression is ...
6
votes
2answers
956 views

Do I really need to use the same private/public key pair in RSA?

So I'm making an Android application, I need my application to be only able to scan my own generated QR codes, and I want to make sure that nobody else can generate fake ones. The data isn't ...
3
votes
0answers
37 views

ED25519 and hierarchical deterministic wallet

I'm building a solution based on the stellar codebase and using the ED25519 curve for the signatures. One of the features I've been adding to the system is a support for hierarchical deterministic ...
4
votes
0answers
60 views

Replacing signer with simulator

Assume we can prove security of digital signature scheme against key-only (no message) attacks. Now we want to prove security against adaptive chosen message attack. We use random oracle model. The ...
1
vote
1answer
30 views

Acceptable condition for dictionary search

I am trying to write a program to break transposition cipher using dictionary search. But I cannot understand the finishing condition of the search. Is there any theory that the maximum number of ...
1
vote
0answers
23 views

Is manually 'salting' my passwords a safe alternative to having a different password for each site? [duplicate]

It is highly recommended to use a different password for each site to prevent the breach of security of one site from compromising the user accounts on all other websites that have the same username - ...
1
vote
1answer
33 views

Generating passwords using Password-Based Key Derivation Function

I was thinking of using different and independent password for different websites, but not storing them in some password manager so I don't need to backup the passwords. I thought I could use some ...
3
votes
1answer
125 views

What do they mean when saying that a certain value should be “super-logarithmic”?

What do they mean when saying that a certain value should be “super-logarithmic”? I've found the Wikipedia definition of a “super-logarithm”, but I'm having trouble understanding how a given value ...
0
votes
0answers
4 views

OpenSSL: Generate ECDSA key and CSR [migrated]

I know how to generate an RSA Private Key and CSR: openssl genrsa -out my.key.pem 2048 openssl req -new -sha256 -key my.key.pem -out my.csr But, How do I do the ...
-1
votes
0answers
27 views

Anyone know of a portion of the Enigma Code? [on hold]

I was reading about it today and it sounds like it would be a fun thing to try to decode. Problem is that I can't find a portion anywhere. Is it classified or am I not looking in the right spots
1
vote
1answer
34 views

Randomized functions cannot increase statistical distance

In these lecture notes instructor Chris Peikert states the following lemma without a proof Let $f$ be a (randomized) function on the domain of $X$, $Y$. We have $\triangle (f(X), f(Y)) \leq \...
3
votes
2answers
185 views

Is the security of MAC function is based on HASH function

It is widely known, generally, that a MAC is a HASH with key. I just want to ensure that my understanding is correct to avoid base further assumptions on wrong conception. So, if I used MAC that uses ...
0
votes
1answer
28 views

In NTRU digital envelope, do everyone know the hash function $H$ used?

I have a simple question about the NTRU original cryptosystem using a digital envelope. The article can be found here: http://grouper.ieee.org/groups/1363/lattPK/submissions/ntru.pdf It is said that ...
0
votes
1answer
31 views

Easily reversible hash functions as a method of data transmission [duplicate]

I've been looking through the literature because I want to see if anyone has implemented this idea I have. I know data compression algorithms work by removing redundancy in data. I was wondering ...
6
votes
1answer
574 views

Is unusual (non power-of-two) RSA key size more secure?

On this blog https://blog.josefsson.org/2014/06/23/offline-gnupg-master-key-and-subkeys-on-yubikey-neo-smartcard/ there is a following sentence Generate master key Below I will use a 3744 bit ...
-1
votes
1answer
64 views

How to calculate this binary operation? [on hold]

I found this binary operation, however It is the first time that I found this operator '.' : That is the equation: 02 • 63 = 00000010 • 01100011 = 11000110 I don't understand how 0 • 0=1 I ...
2
votes
0answers
36 views

How does Bluetooth pairing (SSP with numeric comparison) work?

I have a question concerning the pairing of two Bluetooth devices using Simple Secure Pairing with numeric comparison. The NIST document I am looking at states on page 14: Numeric Comparison was ...
0
votes
0answers
277 views

Changing plaintext for encryption in RSA [duplicate]

In the RSA crypto scheme, the message $x$ (plaintext), is encrypted to produce ciphertext ($y$), by computing $x^e \bmod n$. Of course, that means that $x$ has to be a numeric value for this to work, ...
3
votes
1answer
63 views

PRNG output with truly random noise

I am considering a situation where an adversary does not have access to the $n$-bit output string of a PRNG, but instead receives a noisy version of it, where each bit of the string is flipped with ...
2
votes
1answer
41 views

Choosing between RLWE-KEX methods.

Recently, I've been researching and implementing a bit of post-quantum cryptography, and I came across two RLWE-KEX algorithm for key exchange. The first one, which I implement in my software, is ...
3
votes
0answers
27 views

Computational Randomized Encoding in the hybrid proof

A computational randomized encoding scheme $(\textrm{RE.Encode}, \textrm{RE.Decode})$ works as follows: $\textrm{RE.Encode}(1^\lambda, C, x, r)$: takes as input the security parameter $\lambda$ in ...

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