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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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 $\...
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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: ...
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IV in RSA Encrypted Private Key

I have been provided an RSA encrypted private key which was generated in NodeJS (crypto) using the following: ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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Did the formalization of PKCS#1 RSA key formats come before or after X.509?

The paper introducing the RSA cryptosystem titled "A Method for Obtaining Digital Signature and Public-Key Cryptosystems" was published in 1978. The initial version of X.500 published by ...
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Is RSA-OAEP secure against Shor's factoring algorithm

I've seen in this answer Can Shor's algorithm compromise RSA when both the public and private key are secret? that if textbook RSA is used (deterministic) the Shor's algorithm can reak it. However, if ...
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Does Hinek and Lam's Paper prove that Common Modulus Attacks is possible with non-coprime public exponents?

We know that Common Modulus Attacks work with coprime public exponents $(e',s)$ such that $${e_1}s+{e_2}t=\gcd(e_1,e_2)=1$$ I am reading Hinek and Lam's Paper: Common Modulus Attacks on Small Private ...
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Is it ever OK to to sign RSA messages with padding random bytes?

If a message is padded with cryptographically secure random bytes, is there any reason why this would be less secure than the standard signature padding schemes (PKCS1 v1.5 and PSS)? To give context ...
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Calculate how many possible key pairs exist in RSA [duplicate]

"Calculate how many possible key pairs exist" Found these through searching. Not sure if either are correct. I would've assumed the number would be infinite. phi(n) - 1 phi(n)/2
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How to calculate number of possible key pairs in RSA

What determines the number of possible RSA key pairs for a given $n$? Is it because $\varphi(n)$ produces the number of values that are less than $n$ and coprime with $n$? Is it as simple as $\varphi(...
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How does recovering a message from a signature, as described by RSA, prove that the message was signed with a private key?

In the original RSA paper, in the section that describes digital signatures, the authors write, “He [Bob] need not send M as well; it can be computed from S.” Then, a few sentences later, “Bob cannot ...
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Is it more secure to use Diffie-Hellman to generate a symmetric AES key for use with CBC, rather than use CBC directly atop RSA encryption?

Short question: If we assume a one-session use public RSA keypair on both sides, and if we assume that the input stream will be split into blocks -- with CBC encryption -- is there any security ...
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Does Coron and May's paper for deterministically reducing finding 𝑑 to factoring 𝑛 work with $\lambda(n)$?

Samuel Neves in his reply mentioned a method by Coron and May's 2004 paper for deterministically reduce finding 𝑑 to factoring 𝑛. As you all know, we are using $\lambda(n)$ everywhere now for RSA. ...
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RSA private / public key, two valid private keys? [duplicate]

This might be really stupid but... if P = 11 and q = 13 N = 143 and r = 120 Say we choose e = 7 where gcd(r, e) = 1 and e < r. And therefore our public key is (7, 143) can there be multiple valid ...
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SHA-256 private/public coordinates to the PEM format

I feel that my question might display a bit of ignorance. I have been searching for answers, but have had no luck--perhaps my assumptions are wrong. I apologize if that is the case. Context: I have a ...
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Practical use of semi direct product of group in Cryptography

Is there any example of semi-direct product used in any of cryptographic application? Does it help in choosing integers p, q in RSA?
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Inverse function of RSA and safe prime requirement of DH Key exchange

Ok so the inverse function of RSA encryption (that is decryption) is $ m \gets c^{d}\bmod N$ where $d$ is the secret exponent As I understand the hardness of RSA depends on two things: the Integer ...
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How to generate private SSH RSA key from given primes?

I have two primes and public exponent. How I can generate private key with this values and "ssh-rsa" format?
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A question about RSA key generation algorithm

I'm fairly new to this stuff so be forgiving. I'm trying to learn how RSA works, My resources for the manner of sake: this video this wikipedia page This is what I got so far: since $m^{phi(n)} \...
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What are the rules regarding to numbers in RSA?

I'd like to have a small sanity check first: As far as I understand, diffie-hellman is all about that fact that, given the generator ($g$), the modulo ($n$) and the remainder ($c$), it's hard to find ...
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Uniqueness in modular artihmetic

I'm pretty new in crypto, and studying RSA now. I saw few videos and read about it and how it works. So basically, after we have the modulus N and exponent, we encrypt a message with: ...
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Need help to understand this RSA common modulus attack Python code

I am reading Practical Cryptography in Python. I have problem understanding the common_modulus_decrypt() function. I think the prerequisite of RSA Common Modulus Attack is that two public exponents ...
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Question about SSH host key algorithms

I'm currently writing a report for my Master's degree on the SSH protocol. Quite interesting! However I'm having trouble getting into the inner workings of the host key algorithms. For example, ...
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In RSA, what happens if the plaintext $m$ is not coprime to $n$? [duplicate]

Coming from the Wikipedia page on RSA, I think I understand the following: RSA is based on generating an integer $n$ as the product of two large primes, $p$ and $q$, and encryption/decryption ...
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Decrypting RSA which has no inverse? [duplicate]

Is there any way to decrypt RSA ciphertext $c = m^e \bmod n$ when $\gcd(p-1,e) > 1$?
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What is the public key length of RSA and Ed25519?

I have made some research but doesn't understand fully: In this link, it says ed25519 has a length of 64 characters. Questions: Is this base64 encoded characters? And does ed25519 limit to only 64 ...
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In regard to using RSA-OAEP-256 in JWE to also authenticate token issuer

I'm not an expert on cryptography, so, the understanding below might not be entirely correct. From what I understand, in the context of JWE, the RSA-OAEP-256 key algorithm is meant to provide payload ...
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Any way to prove possession of a RSA 2048 private key using 256 bit?

Alice has a RSA 2048 private key and Bob has corresponding public key. They have a secure connection, but Alice can transmit only 256bit to Bob (Bob can transmit any amount of data to Alice). Is there ...
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What is the overhead of GCM? And how are GCM tags signed by RSA/PKI?

I'm mainly trying to wrap my head around the pipeline of encryption, hashing and signing. I've read over this question, describing the overhead of GCM, which I understand to be configurable for space-...
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More than one private key for RSA

In an RSA-encryption scenario, Bob's public key pair $(n, e)$ is $(143, 43)$. An attacker Mallory tries brute-force and comes to $d = 7$ as the private key. The value of $φ(143) = 120$ is not known to ...
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PKCS RSA - Why do we need encoding [duplicate]

In the RSASSA-PKCS-v1_5 signature scheme, the first step is to perform an encoding on the hashed data. (0x00||0x01||PS||0x00||T). Is this encoding important for security ? What happens if the hash is ...
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Actual RSA encryption & decryption of strings?

$K_{pub} = (n, e)$ $K_{pvt} = d$ Then $E_{K_{pub}}(x) \equiv x^e \mod n$ Practically, when RSA is used to encrypt strings, what is the $x$ here? You cannot take it byte by byte because $\mod n$ will ...
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Textbook RSA signature forgery when e=65537

Searching about RSA signature forgery I came across this question. In the answer, it is stated that for small to moderate $e$ (including $e=3$ and $e=2^{16}+1$, often used in practice), it would be ...
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PGP private key format

I have a PGP Private Key from Bob. ...
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Finding p and q in RSA with a given n, |p-q|<10000

I've got an RSA encryption I need to crack, but to do it I need to find the p and q values of an N I am given - it's quite large, around 308 symbols. I know that N is the product of primes p & q, ...
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Suitable hybrid encryption approach?

I need help for my bachelor thesis. I have a general question regarding hybrid encryption in different ransomware. The hybrid encryption often uses symmetric and asymmetric encryption techniques. ...
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Finding MSB in RSA

Scenario: Alice and Bob send each other encrypted AES (128) messages. In order to change key, Alice has a public RSA key (2049 bits). Bob has Alice's public key. Bob picks a random AES key, encrypts ...
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Why does RSA 1024 provide lower security level than EC256? [duplicate]

And why do we have to use big numbers for RSA? Is it because of some RSA restrictions like p=q=3 mod 4?
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Standard tools for deterministic RSA key generation using seed?

I'd like to resuse the mnemonic I have from bip39 for crypto in other domains such as ssh and tls, etc. Are there standard tools (ie, openssl) to deterministically generate rsa key/pairs given a seed ...
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Relation between factors and their sum on RSA

In RSA and other crypto based on prime factors. If I would know the sum of $p+q$, would it reveal any more information than just knowing $p\cdot q$? Edit: I do not know either $p$ or $q$. The question ...
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What's the preferable encryption for large data and files in terms of speed and security other than AES?

First of all, I'm relatively new to encryption so please bear with me. I'm looking for a way to encrypt large amounts of data only on my device, no need to transfer my encrypted files/data (10-20GB or ...
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Is there a problem with this specific RSA protocol?

So a protocol uses two random primes $P$ and $Q$ with the equivalent bit length of around 2048 bits, multiplies to form $N$. The encryption function in detail is: $m^e \bmod\ N$ $(\text{512-bit-random-...
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Research Guidance on Elliptic Curve Cryptography [closed]

I am a freshman who want to research elliptic curve cryptography. There are a few questions I have: Firstly, I am not sure about how I should narrow down the topic. Where should I focus on? Can I ...

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