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.

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RSA: is it possible for the cube root attack to fail even if e=3?

I've came across an example where the e value is three but no matter what tool/script I try, I can't decrypt it. I'm wondering if the ciphertext and n is super super large, is it possible to crack it ...
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How is RSA key exchange protected against tampering?

The public key is defined by (N, e) where N is the product of two large primes and e is ...
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Is the Key Exchange authenticated and confidential?

I have made a private messaging program and would like to check that nothing is stupid in my use of cryptography. I am an amateur and nothing is for production. I thank you in advance. The message ...
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Is this RSA cryptosystem safe? [duplicate]

Suppose Bob uses the RSA cryptosystem with a very large modulus $n$ for which the factorization cannot be found in a reasonable amount of time. Suppose Alice sends an enciphered message to Bob ...
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Is it possible to verify that the output of an executable came from its unaltered control flow?

I suppose an executable could contain a key which signs its output, but that key could be extracted and used to sign other data. Is it possible to verify that the output of an executable is the direct ...
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Finding an element of $\mathbb{Z}_p$ if the order of that element is known [duplicate]

I have two prime numbers $p$ (1024 bits) and $q$ (160 bits) such that $q$ divides $p-1$. Now I want to find an element $b$ in $\mathbb{Z}_p$ with the order of $q$. That means that $b^q \equiv 1 \mod p$...
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"Electronic signature" legal definition

A proposed California law contains the following definition: (i) “Electronic signature” means an electronic sound, symbol, or process attached to or logically associated with an electronic record and ...
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Would discrete-log-based signing and encryption have been a better choice than RSA?

Diffie-Hellman can be used for key exchange, and can be used as part of an integrated encryption scheme ("DLIES"). Schnorr signatures are possible by relying only on the discrete-log problem,...
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RSA - encrypted plaintext results in the same ciphertext value

Just started learning about RSA cryptography so forgive me if I made any mistakes or misunderstandings. M = 20 be the message that i want to encrypt N = 5*7 , p = 5 and q = 7 φ(N) = (5-1)(7-1) = 24 ...
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RSA: The algorithm aside, how are we turning a string into an int and vice versa?

Let's say that I want to encrypt the file plain.txt. The very first step is actually to turn the contents of that file (lets say it only contains the string "...
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Choice of random in RSA-KEM [duplicate]

This may be nit-picking, I’m not sure so feel free to say so. In RSA-KEM as described e.g. in Wikipedia or this answer, we choose a secret $x : 0 \leq x < n$, and send $x^e \bmod n$ for public ...
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Why doesnt RSA use composite numbers?

I am currently writing a math paper regarding the importance of prime numbers in RSA encryption. I understand that generating q x p = N (where p and q are prime numbers) is simple for a computer ...
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How much work to find such $n$?

Let $W$ be a random $200$ bit number. How much work would it take to find a semiprime $n=p_1\cdot p_2$ such that $p_1,p_2 > 2^{50} $ and $|W-n|<2^{12}$? More generally, let $W_b$ be a random ...
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Using Shor's algorithm to access RSA messages without factoring

Most of the time people forgot that the real aim of the adversary against encryption is accessing the message. For example, in the RSA case, we talk about the factoring of the modulus to reach the ...
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Given $φ(n)$ how can we find any combinations for $p, q$ prime numbers

Suppose i already have found that $φ(n) = 240$ for $n = 900$. How can i conclude that my $n = pq$ is of type $2^2\cdot3^2\cdot5^2$? What is $q$ and what is $p$ here? To be more precise with my ...
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Add a non-signer to an already-signed message

This is a follow-up to the first comment of this answer. A message is signed with the private key of $A$, $s_A$. We know $p_B$, the public key of $B$, but not $s_B$, their private key. Is it possible, ...
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In Rabin-Miller exchange why do we stop when we reach a decimal number and use the value of k that outputted an integer

$773-1=2^k*m$ $772= 2^k*m$ $772/2^k =m$ When $k=1$: $772/2^1 =386 ,$ When k=2: $772/2^2 =193$ When k=3: $772/2^3 =96.5$ When k=4: $772/2^4 =48.5$ so in this case we would use $k =2$ but why ...
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Why bother to generate Key, IV and encrypt them?

When we perform encryption with Public or Private Key, Asymmetric AES with RSA and CBC 128, and when we use the padding as well. Why do we have to bother adding the additional: Key + IV? ...
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Is it secure to use RSA to exchange AES key?

I have to create a Client-Server Application using Java and I want to make the communication secure. I thought to use AES to encrypt the messages and for key exchange I make the next steps: Client ...
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IN RSA encryption why do the values of p and q need to be far apart? [duplicate]

I was doing research into RSA and i read that the prime numbers need to be far apart in order to strengthen the key. Why is that?
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Why can't we use the Zeta function to search for prime factors in RSA?

Maybe I got this wrong, but if the Zeta function is efficient to compute and reverse, and if Riemann's assumption is true (which it seems like), can't we use the Zeta function to efficiently find ...
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Risks of Using SHA1 Instead of SHA256 for RSA with OAEP Padding

I'm presently implementing a simple RSA-based encryption as follows in PHP (using openssl_public_encrypt): ...
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RSA parameter generator algorithm

i'm studying for my basic crypto class and I'm trying to formalize the algorithm for the parameter generation of RSA, unfortunately, I cannot find any algorithm, just plain text. Can someone tell me ...
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How does SSH generate keys for RSA algorithm?

As far as I understood, the core of the RSA algorithm is to have 2 (large) primes ‘p’ and ‘q’, so that ‘n=pq’. Then ‘n’ is the public key, and ‘p’ the private one. The security comes from the fact ...
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Is encrypting every number separately using RSA secure?

Suppose RSA is considered a "secure" method for encryption. RSA is meant to encode a sequence of integers base $27$. If we use an $n=pq$ that is hard to factor, Is it still secure if we ...
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Which of the following is considered cryptographically hard/easy?

Which of the following are easy, if any? Which are hard? and why. Case 1) Given $x^3 \bmod N$, where $N$ is a composite number and we don't know any of the factors of $N$, find $x$. Case 2) Given $x^...
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Building an adversary for a OW-CCA game

Let K_rsa be a RSA genertor with associated security parameter k >= 1024. Let game OW-CCA_Krsa be as follows: How can I build a O(k^3)-time adversary A making at most 2 queries to Invert and ...
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RSA: Is it a security risk if an attacker knows the length of the values of P and Q?

Is it a security risk - or perhaps, how big of a security risk is it - if an attacker knows the length of the values of P and Q used when deriving a value for the parameter N in the RSA encryption ...
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Decrypt AES-128-CBC encypted partial RSA Key

I am given a private RSA key, which header indicates that it is AES-128-CBC encypted. Note that the last ten lines of the key are missing. (This is part of an educational task.) ...
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The number of odd integers we have to test until to find one that is a prime for any arbitrary RSA modulus size

Popular RSA modulus sizes are $1024$, $2048$, $3072$ and $4092$ bit. How many random odd integers do we have to test on average until we expect to find one that is a prime? I know roughly every $\ln p$...
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Is it possible to have a shared secret without any party knowing all the parts?

I believe with Shamir’s Secret Sharing Scheme, I can create an n-part secret and distribute each of those parts to n parties. ...
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Unable to factorise the modulus from public key to extract a private key

I have a public key but struggling to get the modulus from it ...
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Pretty much confused about pretty good privacy-:

Authentication-: I understand that authentication is basically digital signature. But what I don't understand is how it has been explained here specially the RSA key part. It is leading me to huge ...
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How to decrypt a file using RSA and just a public.pem file?

I have an encoded file and a public.pem file. Is it possible to decode the file using the public.pem file or do I have to start looking at private keys? I tried https://github.com/Ganapati/RsaCtfTool ...
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Would being able of factoring integers efficiently have some consequences over Elliptic Curve Cryptography?

Let's assume you can factor integers in a very efficient manner. Would that endanger the security of e.g. elliptic curve cryptography, or is there no link between the two ? You can often read that ...
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conflicting definitions for dP / dQ and exponent1 / exponent2 in PKCS 1?

In Section 2 dP and dQ are defined thusly: ...
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Eavesdropping attack on text-book RSA encryption with public nonce

Consider the following scenario: Alice has a secret key and public key pair for text-book RSA (denoted $\text{sk}$ and $\text{pk}$ respectively). Bob has an authentic copy of $\text{pk}$. The ...
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How is this step being calculated and why is that getting the factors is able to determine private key or universal forgery?

https://link.springer.com/content/pdf/10.1007/3-540-49649-1_18.pdf In class I, why (4) implies $g\equiv 1 \mod q$ Also even though I get $p$ and $q$ it still can't get $ord_n(g)$ without trying out ...
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How to find iteration exponent in a cycling attack?

In Simmons and Norris paper they demonstrate the cycling attack with the following example: p = 383 q = 563 s = 49 and t = 56957 ( a prime) The attacker knows the publicly available r = pq = 215,629 ,...
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How to ensure the data comes from verified source without using asymetric encryption

I'm building a project that is remotely controlled using LoRa and I want to ensure, that nobody can imitate my transmitter and send packets to my receiver. Just encrypting sent data is not enough ...
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Question about white-box rsa algorithm

I found a scheme for white-box RSA. It seems to protect the input and output of modular operations. I'm curious about how to analyze the security of this solution. Does anybody know anything about it?
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Why is confusion and diffusion never talked about in asymmetric crypto?

While talking about symmetric encryption schemes like AES we always have a goal of achieving confusion and diffusion. But when it comes to asymmetric encryption schemes like RSA, DH etc. we never talk ...
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No Final subtraction in Word-level Montgomery Multiplication

I am trying to make an RSA module in VHDL, which in turn will be deployed to an FPGA. I am trying to implement a full Montgomery algorithm which means that I am working with the Montgomery ...
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Comparing complexity of RSA decryption with/without CRT

(Cross-listed on math stackexchange, received no replies) For context, this is a homework question from an assignment already turned in. I am looking for better understanding of the concepts involved, ...
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What are those RSA Challenges, DES Challenges and RSA Factoring Challenges

Can someone explain the differences between the DES challenge, the RSA challenges, and the RSA factoring challenge? What were the aims? I think the factoring challenge was to encourage research, the ...
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Why does Shamir's Trick for RSA Work

I have read that Shamir's trick can protect RSA with CRT against fault attacks. However, it is not clear to me why the following equations $$ s_{p}^{*}=m^{d \bmod \varphi(p \cdot t)} \bmod p \cdot t \\...
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Multiuser encryption, singleuser decryption [duplicate]

I have an hybrid encryption (RSA, AES) for a file sharing project I am working on, where I use a single public key for encryption on the sender side and corresponding private key for decryption on the ...
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Is there an easy way to make textbook RSA secure enough so it can be used in real life?

I have written a raw (textbook) RSA implementation (just for fun) and I wonder is there an easy way to make it secure enough so it can be used in real life (without implementing OAEP+ and RSASSA-PSS)? ...
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Simple Key Exchange, One Server

I am trying to better understand how TLS works. I understand in the normal use case you need various random values generated and used in the key exchange, to prevent some MITM reusing a previous ...
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Does the signature length of RS256 depend on the size of the RSA key used for signing?

The following NodeJS code, when run (v16.8.0), logs 512 to stdout. ...

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