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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With node-jose, Should I expect the JWK -> PEM conversion to be reversible?

I am using node-jose to convert a particular JWK to a PEM, and then ... converting that PEM to a JWK. The resulting JWK has the same e, but different n than the original. Should I be surprised? I ...
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RSA: Construct private / public key for given cipher and plain text message

let's say we are given a classical RSA encryption scheme, though we would like to "reverse" the task: Given two messages $c, m$ choose $p, q, e$ such that $p, q$ are prime and $c ^ d \equiv m\pmod N$ ...
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RSA with a prime substituted by a Carmichael number

If the public key in a RSA system is $(n,e)$ with $n=pq$, $p$ prime, $q <p$ a Carmichael number and $\gcd(e,(p-1)(q-1))=1$ then if $d$ is the inverse of $e$ modulo $k=(p-1)(q-1)$, I want to show ...
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Private exponent on RSA key

this is the first time I write here. I'm studying a library to encrypt/decrypt with RSA algorithm. In an example given by the library I found this: ...
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I don't understand RSA encryption (specific questions)?

So I've been studying RSA for a class and I'm having a hard time understanding how it works. Why do we choose the value of e such that e is relatively prime to the totient (as opposed to just being ...
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(Cracking RSA) How to calculate the Private Key using Public key, p,q,r,n?

I have been given the following values : ...
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Accidently deleted “~/.gnupg/pubring.kbx” , how to recover keys [migrated]

is there is any way to recover the encryption keys in this case, since they really important 1) the issue: i've lost my gpg key identifiers by deleting ...
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Can there be more than one valid private exponent for a given p, q, and e in RSA encryption?

For example, given: p = 173, q = 149, e = 3 Using phi(n) gives d = 16971 While using lambda(n) gives d = 4243 Both values satisfy the checking equation (de)%phi=1, so are both correct, and if so, ...
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Encrypt and decrypt data accessible by two users on the web on multiple devices

I am currently building a website where a user will be able to upload a file to my server and another user will be able to download the file. Now i want to add encryption to this with the following ...
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Relation between signature size and message-digest length in RSA PKCS#1v1.5 sign/verify

When using RSA-PKCS#1v1.5 to sign and verify a message-digest, is there a compulsory relation between the sizes of message-digest and the key/signature ? For example, If I use key/signature length of ...
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Exclusion proof cost

I am trying to understand what is the cost of non-membership verification for a universal accumulator? More specifically, how can I compute it? Whether using an accumulator is more efficient than ...
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Factoring $n$ in RSA knowing $e$ and $d$

I know that if $(n,e)$ is the public key in RSA and we also know $d$ the private key, then there is a probabilistic algorithm to factor $n$. I'm reading the proof from Fact 1 on here. I understand ...
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Common modulus attack with not coprime exponents

lets suppose we have the public keys $(n,e_1)$ and $(n,e_2)$, such that $\gcd(e_1,e_2)=d>1$, and the same message encrypted with these two keys. I'm trying to see if common modulus attack on RSA ...
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Constructing an integer with specific totient without factorization

Given $N(=pq)$, but not its factorization. Somehow you manage to know, that $k$ divides $\phi(N)$. Is it possible to come up with an integer $N^{*}$, for which $\phi(N^{*})=\phi(N)/k$, without ...
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Is HTTPS encryption using the RSA algorithm?

According to this article HTTPS and RSA is the same thing: https://tiptopsecurity.com/how-does-https-work-rsa-encryption-explained/ From other sources I learn that they are both asymmetric encryption ...
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Prime Factorization in RSA always leads to the product of two primes?

Lets prime factorize $30$: $$30 = 3 \cdot 10 = 3 \cdot 2 \cdot 5$$ We see that the number $30$ is a product of $3$ primes. But in RSA, when factorizing huge numbers, we always seem to only get two ...
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What is meant by the duality and homomorphism of an encryption algorithm?

I am new to the field of cryptography and security so spare me with this question. What is the general idea of duality and homomorphism of an encryption algorithm? And how one may prove those two ...
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Why is Multiplicative group used in RSA or Euler's theorem but not additive?

I am on the verge to understanding RSA, but suddenly a question popped into mind. When we are calculating $U(N)$ i.e $U(PQ)$, we are taking invertible elements that are co-prime to $N$. For example, $...
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JWE between Android/iPhone and backend

I'm working on a solution where JWE is needed between an Android app and a backend written in Node.JS, using node-jose. I've been struggling a lot since it seems ...
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What's the actual difference between RSA encrypting and Descrypting and RSA Signing? [duplicate]

this question arised because I'm working with Windows' CNG library and it has 4 functions for RSA: BCryptEncrypt (private key, message) BCryptDecrypt (public key, message) BCryptSignHash (private key,...
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FLT is partly applying to RSA equation, and also relation between ED mod phi and Phi + 1 mod N

After numerous attempts from myself and all of you guys, I finally came to understand RSA. I can now prove it and understand how I got there. But I still have some very few polishing questions. 1) We ...
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Protocol for proof of knowledge of $l$-th root

Assume we have Group G in which the adaptive root assumption holds. This assumption states that if we choose an element $w$ and after that, if we receive a prime value $l$ it is hard to find the $u$ ...
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Relation between $N = P \times Q$, and $\Phi(N)$

When studying RSA, and proving simple concepts to myself, I went and understood groups and rings, but I failed to understand Lagrange's theorem. I did understand how from invertible finite groups I ...
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Proof of two pairs with same exponent

Lets assume we have a group $G$ with unknown order. And we have a pair $(A_1,K_1), (A_2,K_2)$ in which all $A_1,K_1,A_2,K_2$ are group elements. The claim is $A_1= K_1 ^ x$ and $A_2 = K_2 ^ x$. or ...
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What is blindness and forgeability in chaum blind signature scheme?

I am going through the voting protocols. I know how blind signature works (Blind Signature), but why is blind signature - unconditionally ”blind”, conditionally ”unforgeable" (as highlighted in the ...
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Cryptography question(s) about RSA [duplicate]

In the real world, it's best to use at least two or more algorithms to encrypt data. From what I know, RSA acts as a wrapper to transfer data safely across web systems or API(s), or acts as a wrapper ...
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Enforce weak RSA in TLS

I'm going to give a small talk on the mathematical background of RSA. My audience will consist mostly of software engineers and to make the mathematical stuff tangible, I wanted to demonstrate how to ...
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Scheme to verify AES key was correctly encrypted for public key recipient

In our file sharing scenario there are three participants: $A$, $B$ and $C$. Each participant has a public-private key pair (let's assume RSA for now). $A$ wants to share a symmetric AES key $k$ with ...
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Relationship between $N$ and $\phi(N)$ in the RSA algorithm

Recently I started learning how the RSA algorithm works and there is one single part of the computation which really confuses me and can't get over it. Let's say I chose 2 prime numbers, namely $P ...
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RSA. Would someone kindly help me understand what d and c are in this factorization exercise?

What are $d$ and $c$ in this factorization exercise? What order must $d$ and $c$ have for $p$ and $N$? If $N=pq$, $(p+q-4) =0 \bmod 8$, and $p \geq (p+q)/4$ $$N=66390187$$ $$(3*N-1)/8=24896320$$ ...
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How to decrypt using CRT, and then verify by encrypting without CRT?

Here is the actual question that I need to answer: An RSA encryption scheme has the set-up parameters $p = 31$ and $q = 37$. The public exponent is $e = 17$. Decrypt the ciphertext $y = 2$ using the ...
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RSA Decryption: Doubts: knowing p or $\phi(n)$ can lead to find private exponent?

I have some doubts about RSA (the public key $n$ and $e$ is public): Note $n = pq$ and $\phi (n) = (p-1)(q-1)$ 1) Say if some hacker knew $p$, why would it be easy for them to find $q, \phi (n), d$? ...
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Can the knowledge of the inverse of $p$ modulo $q$ help factor $n=pq$? [duplicate]

With the RSA algorithm implemented using the Chinese Remainder Theorem (CRT), the private key has to be provided with not only $p$, $q$ and the private exponent $d$, but often also with the pre-...
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Message input format for RSA algorithm

I was trying to implement the RSA algorithm myself. I have written the key generation part. My question is if I have the word "apple" which I want to encrypt, do I have to convert each alphabet to ...
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Licensing software with asymmetric signed files

NOTE: I know that there are numerous topics here on StackExchange about this but I've read them all and this question still persists. I'm currently working to enhance the security of a windows based ...
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What algorithm for AES key wrapping to choose in an embedded environment

In an embedded environment, what AES key wrap algorithm is best, in terms of performance and security coverage? We are using RSA PKI asymmetric encryption.
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Binary verification of application image before loading it into DRAM

Working on a boot process where the application image has to be verified before loading it into DRAM. We found 2 strategies; RSA-1024, where the private key is secure in premises and the only public ...
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Why is there no “ephemeral non-DH EC” key exchange in TLS?

In RSA key exchange, the client picks a premaster secret and encrypts it with the RSA public key in the server certificate, and sends it to the server. This offers no forward secrecy. In ECDHE key ...
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number theory question in a group with unknown order

I was reading a paper and I am struggling understanding one part of it. Lets say we have a group $G$ of an unknown order $n$. we know that $B<n<B+C$. both B and C are large values). we choose a ...
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Is there an asymetric encryption whos output size is quite equal to the input size

I want to verify, that a chunk of data which has a size of around 16 bytes is sent by me, by simply encrypting it via a private rsa key, providing the public key in the source code for the ...
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Why can't ransomware practically use RSA to encrypt all files?

I understand that a few ransomware have used an RSA public key to encrypt all files belonging to the victim. This is a bullet-proof system in terms of its security because the private key is always ...
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A number theory problem in RSA

Let say we have $N=pq$ (Both $p$ and $q$ are safe primes, meaning $\gcd(p-1,q-1)=2$) let's assume $e$ is an odd number which can be efficiently factored and assume that we know the $e$'th root of 1 ...
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Information security evaluation

I saw this exercise for evaluating the security(confidentiality, integrity, authenticity, and non-repudiation) of some schemes: ENC(M) || SignA(ENC(M)) ...
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RSA Signing: SHA512 incompatible with PSS?

I am wrapping the RSACng class from the .Net API. Whilst unit testing, I run checks against an array of possibilities: Key Size = 1024, 2048, or 3072 bits Padding ...
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SHA-3 for Integrity

We used to use CRCs to check the integrity of files. For safety analysis we could associate a probability for detecting a corrupted bit in a large file. Now we are using an RSA Signed SHA-3 hash for ...
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Can a 3rd party decrypt static Diffie Hellman?

Do cipher suites that use static Diffie Hellman (not Ephemeral) allow for the same 3rd party decryption ability as RSA cipher suites? With RSA key exchange, 3rd parties can gain possession of the ...
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What is the Bilinear-map accumulator disadvantage

Bilinear-map accumulator [1] is more efficient than the RSA accumulator [2] but do you know any disadvantage for the bilinear-map accumulator when compared to RSA accumulator?
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Exponentiating big numbers for RSA operation

I am following the book "Network security private communication in a public world - 2nd edition. Section 6.3.4.1 Exponentiating big numbers. base = 123, exponent = 54, mod = 678 What I understand is ...
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Can we break RSA with an optical Fourier Transform?

We all known that RSA can be compromised using quantum Shor's algorithm. The horsepower underlying this algorithm is the Fourier transform. However, we can use alternatives to perform this function, ...
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Is it possible to generate a membership proof using an RSA accumulator without knowing all the accumulated values?

I am currently learning about RSA accumulators and this was just a question I had since in most available implementations I see in Github accumulated primes are stored in hash tables and they are ...

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