Questions tagged [rsa]

An asymmetric (e.g. public-key) cryptosystem, based on modular exponentiation with big exponents and modulus. RSA can be used both for signature and encryption with proper paddings.

Filter by
Sorted by
Tagged with
2
votes
1answer
53 views

Commitment schemes for arbitrarily large integers

My question is about commitment schemes for arbitrarily large integers. One scheme I know uses groups of unknown order (RSA or class group) and depends on the strong-RSA assumption. You chose a random ...
1
vote
1answer
68 views

RSA proof regarding m % n

I have a question regarding the proof that RSA works I understand that $m^{(ed \bmod z)} \bmod n = m \bmod n$ , but I don't understand why $m \bmod n = m$ (This question assumes m is the message, $z=(...
-1
votes
0answers
42 views

an RSA puzzle that i need help to solve

alice has three friends bob , carol and david , their public RSA keys are (3 , n1) , (3 , n2) and (3 , n3) (e is 3 ) respectively (n1 , n2 and n3 given to you ) . now alice encrypts the message M ...
1
vote
0answers
32 views

RSA with Carmichael number

I've to prove that RSA still works with a public key $(e,pq)$ where p is a prime and q is a Carmichael number such that $q<p$ and $\gcd(e,(p-1)(q-1))=1$ I know how RSA works wiht $p,q$ primes but ...
-1
votes
0answers
37 views

Is any of this new? or is it already well established knowledge? [closed]

I have done some research into the functions a^floor(x) mod p floor(x)^e mod n and wanted to share my results and see if this is new to anyone? Here is a pdf of it in a nice format (can be viewed ...
0
votes
2answers
76 views

How can a recipient recognize which encrypted messages are intended for them?

Let's say there's a decentralized email service where parties' public keys are known. A sender sends a message to a recipient by encrypting via RSA with the recipient's public key and posting the ...
0
votes
1answer
43 views

Why is $\phi(N) = (p^2 -1) (q^2 - 1)$ here?

I was reading a paper on attacks on RSA variants, and the paper equates $\phi(N) = (p^2-1)(q^2-1)$. Before, I have always seen $\phi(N) = (p-1)(q-1)$ and don't understand why it is different here. I ...
1
vote
1answer
47 views

RSA message encryption question

I'm very new to cryptography, I wanted to know what exactly do I have to do to encrypt a three-letter message using RSA? for example if I wanted to encrypt this message $M= \text{HCP}, p=11 q=13$. Do ...
1
vote
1answer
79 views

Faster alternatives to RSA trapdoor permutation

We're working on web3.0 decentralized internet, a big part of which is a decentralized file storage system where clients upload files to storage providers and pay them for the services. Storage ...
0
votes
1answer
64 views

is this useful to help break RSA?

So, I'm kinda newbie in this cryptography stuff, I just like to understand complex things.A couple of months ago I was learning and I maybe found a pattern in prime numbers and their multiplications, ...
1
vote
1answer
32 views

What if the bitlength of the value evaluated in Barrett reduction is greater than 2k the modulus?

For $c\equiv a \pmod n$, in Barrett Reduction, $\mu = \lfloor{\frac{2^{2k}}{n} \rfloor}$ is precomputed, where $k = \lceil{\log_2{n}} \rceil$ and the bitlength of $a$ is assumed to be less than $2k$. ...
0
votes
1answer
96 views

Chosen Ciphertext Attack textbook RSA

I'm trying to perform a chosen-ciphertext attack against an RSA oracle. I have $c$ as the ciphertext I want to decrypt, $e$ and $n$. I already know that I could choose a number $r$, compute $r^e \cdot ...
0
votes
0answers
64 views

An “unsafe” curve over RSA? [duplicate]

I'm implementing a token server and considering backing them with ECDSA. The options from the library I'm using expose the NIST curves P-256, P-384, and P-521. The safe curves site does not list P-521,...
4
votes
5answers
3k views

Why do we use groups, rings and fields in cryptography?

I'm a student of Masters in Cyber Security. I have a habit to understand things from their first principles (at the very beginning). Kindly use any simple mathematical example to answer because I have ...
4
votes
1answer
112 views

Factorization for special primes $P$, $Q$, and $R$

Suppose that $p$, $q$, and $r$ are distinct $n$-bit primes, we define $$ \begin{array}{rcl} P & = & p \mathbin\Vert q \\ Q & = & q \mathbin\Vert r \\ R & = & r \mathbin\Vert p \...
0
votes
0answers
26 views

CNG/BCrypt/NCrypt Import an ephemeral AES key wrapped with a persistent RSA key

I will write some kind of security client/server pair: The server part provides wrapped AES keys. The client part, based on CNG win32 API (ncrypt.h+...
2
votes
0answers
53 views

How to associate a post-quantum public key with a pre-quantum one in blockchains?

As a layperson, I'm curious if a cryptocurrency could fork to a quantum-resistant algorithm without people losing access to their wallets. Is it possible to generate a quantum-resistant public key ...
0
votes
1answer
38 views

In a hybrid cryptosystem is safe to send the encrypted key together with the encrypted message?

I am encrypting a message using an hybrid cryptosystem: I encrypt my message using AES-256 and I encrypt the symmetric cipher key using RSA. The following questions come to my mind: I want to know if ...
-2
votes
1answer
121 views

How can I find d knowing c, n, e in RSA?

If I know $n,e,c$ can I find $d$ in RSA? ($n = 3174654383$ and $e = 65537$ $c=2487688703$) I saw this $d=(1/e)\bmod\varphi$ but if the numbers are getting bigger it can be hard to get $d$ in that way ...
-1
votes
1answer
132 views

Can Big Data together with deep neural networks attack RSA by affording the vast calculation of prime multiplications in advance?

This is a spin-off from Can Big Data attack RSA by just calculating many prime multiplications in advance? [duplicate]. Intro I am somewhat new to cryptography. Repeating the basics of RSA from How ...
0
votes
0answers
64 views

Attack a RSA padding scheme that appends zeros

Imagine we implement RSA padding such that a number of byte zeros are appended to the message until its length is equal to 100 (i.e. 800 bits). Also, let's assume that the public exponent $e$ is equal ...
0
votes
0answers
77 views

Can Big Data attack RSA by just calculating many prime multiplications in advance? [duplicate]

Intro I am somewhat new to cryptography. Repeating the basics of RSA from How are the primes used to generate RSA keys?: Textbooks say the one-way function is merely two primes (with some critical ...
3
votes
1answer
109 views

Order of random element in RSA is big

Im trying to understand the proof in "The Discrete Logarithm Modulo a Composite Hides O(n) Bits" by Håstad et al, where he shows that the order of a random element in RSA group is big. I got ...
2
votes
1answer
95 views

Can you break an RSA modulus if you know $k \cdot \phi(n)$ where $k$ is a large prime?

Given some RSA modulus $n$, can you factor $n$ if you are given $k \cdot \phi(n)$ where $k$ is also a large prime? (Of course, you could factor $n$ if you were given $\phi(n)$ as discussed here, but ...
0
votes
1answer
80 views

RSA Inverse Multiplication

I have $n,e$ and $c$, $p$ and $q$ are prime, but $q$ is the inverse multiplication of $e$ and $p$ so $$q = e^{-1} \bmod p$$ How can $i$ get $p$ and $q$ back?
2
votes
1answer
104 views

Are GPUs inefficient for calculations on big numbers? Is RSA and EC cypto generally done on CPU only?

Looking specifically at RSA and EC algorithms which imply doing operations on integers >= 256 bits (>> 64 bits), I have noticed (from my limited experience) that 99% of the software for ...
0
votes
0answers
59 views

Request for a zero-knowledge proof (or hint)

I want to design a zero-knowledge proof (ideally a NIZK, but could be a sigma protocol) so that Alice can prove that a certain encryption contains a value that has been signed by a certain key. More ...
0
votes
2answers
74 views

RSA decryption time

I'm currently trying to create a lua script that can handle encrypting and decrypting using RSA, but when decrypting, the program takes an extremely long time, whilst when encrypting, the program is ...
0
votes
2answers
96 views

Do perfect squares count as valid moduli for an RSA semi-prime?

The question is pretty self-explanatory but basically I just want to ask if, when choosing the p and q primes that, when multiplied, become the modulus for an RSA public key, is there a risk that ...
5
votes
1answer
487 views

What is the Lord of the Ring(s): Side Channel Attack and What are the results

A recent Paper to appear on USENIX Security 2021 titled as Lord of the Ring(s): Side Channel Attacks on the CPU On-Chip Ring Interconnect Are Practical by Riccardo Paccagnella Licheng Luo Christopher ...
0
votes
1answer
76 views

Example of breaking RSA with CRT [duplicate]

I understand that if the same message is sent to 3 people with $e=3$ that even with different public keys, the message can be decoded using the Chinese Remainder Theorem. I have tried to figure out ...
0
votes
0answers
45 views

Why if i change some characters of a Public key on authorizedKeys the login still works

This question is similar to: [1] Why does my SSH private key still work after changing some bytes in the file? But in this case (on Windows) after editing the authorized_keys file and changing some ...
1
vote
0answers
36 views

Combining ECC And RSA for a Web Based Chat system

I'm a building a Web application chat message system(Over TLS) and i would like to know if the following theory is correct. Sender I'm generating keyPairs using RSA and another KeyPairs using ECC. By ...
1
vote
1answer
46 views

What is the NTRU parameter equivalent to security level 112, 128 and 192?

I came across this paper which mentions this table, which states that NTRU 347 is equivalent to 112 bit security level However, in this paper, Choosing parameters for NTRU mentions that NTRU-401 is ...
2
votes
3answers
149 views

Factoring Anderson's RSA backdoor

In 1993, Anderson [1] proposed a backdoor to the RSA key generation algorithm. This backdoor requires that a backdoor key (prime) $A$ be implanted within the key generation portion of the RSA ...
1
vote
1answer
55 views

Reveal a plaintext with 3 encryptions of Textbook RSA

Assume we using Textbook RSA encryption with the public key $(N,3)$. How can I learn message $m$ if I have the encryptions of $m,m+1,m+2$ in an efficient way? I'm studying for a test and it's a ...
0
votes
0answers
45 views

Guarding against vulnerabilities for a digital signature service (RSA )

Lets's say I have a cipher-module / cryptography-service that signs a hash of some unknown payload. What are the possible attacks that I would need to guard against in this context (primarily assuming ...
88
votes
4answers
38k views

Does Schnorr's 2021 factoring method show that the RSA cryptosystem is not secure?

Claus Peter Schnorr recently posted a 12-page factoring method by SVP algorithms. Is it correct? It says that the algorithm factors integers $N \approx 2^{400}$ and $N \approx 2^{800}$ by $4.2 \cdot ...
0
votes
0answers
36 views

Can RSA key be determined when encrypted text is displayed alongside the clear text?

I would like to encrypt some text and display part of the encrypted text alongside the clear text as a means to prove that I generated it. For example, let's say I have the text ABCDE that I want to ...
1
vote
1answer
25 views

Where does the range of possible values in Bleichenbacher's attack against PKCS #1 come from?

In Bleichenbacher's paper on his attack against PKCS #1, we find: If the oracle says that $c'$ is PKCS conforming, then the attacker knows that the first two bytes of $ms$ are $\mathtt{00}$ and $\...
1
vote
1answer
134 views

Can an altered RSA private key still work as the original?

I am interested in understanding public-key encryption using RSA. On the Khan Academy website, I noticed an anomaly when testing out the tutorial. I created the following public/private keys: ...
0
votes
1answer
54 views

IV in RSA Encrypted Private Key

I have been provided an RSA encrypted private key which was generated in NodeJS (crypto) using the following: ...
4
votes
1answer
127 views

Why does PGP still use the Fermat primality test? What if it hits one of the Carmichael numbers?

Since the Fermat primality test is not very reliable, most applications use it for pretesting only. Wikipedia says that PGP still uses it: Another well known program that relies only on the Fermat ...
0
votes
1answer
26 views

Generating a SHA256 pkcs1v1.5 Blind RSA Signature using Chaum's Blind Signature Scheme

I am a noob to cryptography in the sense that I have very less understanding as to how RSA encryption schemes work in practice. However I do understand the theoretical foundations of RSA cryptography ...
0
votes
1answer
31 views

Using a RSA signature to confirm the sender of a physical letter?

(1) Alice wants to send Bob a physical letter. (2) Alice also wants Bob to be confident that she sent the letter and not an imposter. (3) Alice is confident that a potential imposter will not be able ...
1
vote
2answers
63 views

Is PyCryptodome's export_key with passphrase secure?

When exporting a private key with PyCryptodome, DER format, PKCS#8 and a suitably strong passphrase, is the resulting exported key secure enough to place somewhere that you would not normally want ...
0
votes
0answers
32 views

Best model for client software encryption / decryption

I would like to develop a small solution (c#) that must secure data exchange with an untrusted server. The model is that this software will run on a Windows client then Encrypt data before pushing it ...
2
votes
2answers
133 views

How to handle modular arithmetic with regard to two's-complement negative numbers?

The reason for asking, is that this occurs in real life with CRT calculation of RSA decryption/signing. In CRT RSA, there's the need to calculate subtraction, and it's known negative numbers could ...
2
votes
1answer
84 views

Fake non-membership proof in RSA accumulator

As explained in this answer, if one knows the trapdoor (factorization of modulus $N$) in an RSA accumulator, one can generate fake membership proofs. Does the same apply to non-membership proofs? More ...
0
votes
1answer
48 views

RSA key requirements so that it can decrypt a DES key

I came upon a solved exercise that uses a client's RSA key to encrypt a DES key. It has the following phrase: value of n for RSA key generation has been chosen accordingly so that the DES key can be ...

1
2 3 4 5
46