# Tagged Questions

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.

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### Why is RSA still being used? [duplicate]

In hybrid encrytion, I still see that some site's use RSA in their https connection, so now I wonder, why do they not use ECC instead of RSA, ECC requires less computational power and encrypt's and ...
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### Diffie-Hellman combined with DSA/RSA

we have learned Diffie-Hellman, RSA and DSA (Digital Signature Algorithm) in university. Because DH is vulnerable of Man-in-the-Middle we had the task to program the DH combined with RSA to protect ...
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### How to encrypt huge data using RSA? [duplicate]

Is there any way to encrypt the huge amount of data using RSA? I was supposed it is possible but when I read some articles what I saw is that, this is bad practice or they say can only encrypt bit ...
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### RSA PlainText without Knowing Private Key

I couldn't solve this problem for three days... In RSA, [n = 13, 19] [e = 3] c1 = m^3 = 83 mod 247 [e=5] c2 = m^5 = 97 mod 247 then, use ...
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### What is proper size of window Using RSA Window method?

I want to Use Window method for RSA modular Exponentiation. because of SCA. But I don`t know what is proper window size.
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### How to decrypt an RSA ciphertext given an oracle providing the lower 8 bits of decryptions?

I have access to an oracle that can encrypt and partially decrypt a number with RSA-1024 algorithm. For encryption: $$C = M^e\bmod n$$ But for decryption, result will ...
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### Securely register a client in server using AES an RSA

I've designed the following protocol to send the client's public key to the server. Initially, the client knows server's public key, but the server does not know the client's public key. client ...
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### How to use the hardcoded server's public key to register a client application?

I'm designing the security for a smartphone app that can be used to make car reservations. Clients have to register them with their driver's licence through the application and can then book a car. ...
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### Is AES-256 bit encryption secure against this kind of attack? [duplicate]

Recently I came across this article. http://www.cs.tau.ac.il/~tromer/acoustic/ Could this put all computers at risk for decryption?
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### Weaknesses of RSA for $e_A\neq e_B: \gcd(e_A,e_B)=1$ [duplicate]

If two people, A and B, are using a common RSA modulus N, and they select distinct exponents $e_A$ and $e_B$, such that they are coprime, why does this mean that someone can decrypt (in polynomial ...
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### How common are non-RSA digital certificates?

Is there a statistic available that shows just how common are DSA or ECC certificates amongst webservers? I know that RSA-based certificates are the most common, however I'd like to know, if there is ...
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### RSA encryption with private key, decryption with public key (again)

First of all let me point out that I am aware of all the theory behind asymmetric encryption and signing, and other related areas like signcryption, etc. It seems that mathematically it is possible to ...
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### Large Volumes of Asymmetric Encryption

First of all, I apologize in advance if I use any incorrect terminology. I am just getting my feet wet when it comes to cryptography and there is a lot to learn. For the past 12 months we have been ...
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### Encoding issue - PKCS#11 CKM_RSA_PKCS wrapping unwrapping EME-PKCS1-v1_5

I am trying to figure out why I am not able to get compatible format of EME-PKCS1-v1_5 3DES key encrypted by public RSA key. I need to send to a third party 3DES key encrypted using their public RSA ...
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### Proper forward secrecy [closed]

Currently I have a protocol using a simple RSA to AES handshake. I have been reading more and more and would like to implement proper forward secrecy, but at the same time I'd like to improve the ...
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### Is RSA safe anymore? [duplicate]

Some people may have heard of Shor's algorithm. It allows for integer factorization on a quantum computer. This wasn't a problem a little while ago since we didn't have any quantum computers. Google ...
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### RSA : Double-Encryption and order of Encryption

I'm studying cryptography and we're looking at RSA. We're required to do a double encryption from Alice to Bob and then Bob back to Alice. We've been told the order of encryption is important and it ...
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### Complexity using RSA

You encrypt a message using the RSA encryption system as $t^e \pmod n$ , where $t, e < n$ and $t$ is the numerical equivalent of the message. The message is written in a $27$-letter alphabet and is ...
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### splitting the plaintext and ciphertext into blocks

Say I was to use RSA with a given value of n. I choose to split the plaintext and ciphertext written in a 27 letter alphabet into blocks with k and m characters resp. How would I find the largest ...
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### How to calculate Private Key in RSA using Extended Euclidean Algorithm [duplicate]

I have googled for about 2 hours now and still haven't found an explanation. The wiki article just makes me more confused and so has every other similar question I've found on StackExchange. Here's an ...
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### How to generate a bilinear group of prime order p [duplicate]

I am trying to implement an IEEE Paper In Cryptography. I read many reference regarding an RSA key generation. But i am confused with above statement. Please someone explain me What it says with ...
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### Strength of a cryptography algorithm [duplicate]

I'm just read this article from Atmel corporation in comparing RSA with ECC cryptography algorithms. First of all please read these two paragraphs quoted from the article: P1: Strength of an ...
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### How to decrypt RSA cipher text? [closed]

How can I decrypt an RSA cipher text in which I am only provided with a public key and the cipher text. The person who encrypted it made a mistake in taking the exponent.
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### File encryption using per-user-encrypted shared key

So I'm looking to encrypt files using AES CTR, using a shared key which would be accessed via a per-user password. My two main concerns are: - making sure that the algorithms in use are appropriate ...
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### Understanding RSA [duplicate]

I'm reading RSA in Cryptography Course. There is portion of RSA that's confusing me. In Handbook of Applied Cryptography its written Represent the message $M$ as ...
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### Values of p and q when e = 3 (RSA)?

I am doing a paper on textbook RSA (this is for high school btw) and in my example I need two very large primes, but I want my $e = 3$. Is there a short way to calculate the values of $p$ and $q$ ...
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### public/private key: is it possible to have master public/private key

This may be a very primitive question which might not be possible but I have this question to understand. Assume Yahoo provides a messenger where yahoo users can chat in secure way (end-end ...
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### In the RSA encryption system, are there not multiple messages m that give the same cipher text c? [duplicate]

For example: p = 5, q = 11, n = 55 $\phi$(55) = 40 e = 3, $\phi$(55) and 3 are relatively prime m = 3, then: $3^3 mod(55) = 27$ m = 113, then: $113^3 mod(55) = 27$ I heard that e and $\phi$(n) ...
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### RSA Encryption: What happens if n is a factor of the message M? [duplicate]

From what I have learned about RSA encryption, the message M and the modulo n must be coprime because Euler's theorem only holds for coprime numbers? for example, what happens if I choose p = 3, q = ...
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### RSA-PSS salt size in certificate

In RFC 4055, the signature RSAPSS algorithm has the following ASN 1 parameters: ...
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### PK systems using groups in practice

The four Public-key cryptosystems: RSA, ElGamel, DH, and Rabin (all with others) all require some group operations in an integer field or multiplication group of some residue classes. When it comes ...
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### RSA: If I sign the same digest with same key twice, will the signatures be identical? [duplicate]

If I don't have public keys to verify the signature, can I use this to discover that two signing services are using the same key? Can you send a reference?
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### What is the danger if a non-prime is chosen for RSA? [duplicate]

I was reading this question about generating primes for RSA keys. The answers point out that most implementations of of the algorithm use probabilistic prime-ness checking algorithms. The answer by @...
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### Two questions on EMSA-PKCS1-v1_5

If I implement EMSA-PKCS1-v1_5 in the following two non-standard ways, what kind of things could go wrong? The padding structure will be referred as (00|01|PS|00|DER(Digest Algo)|Digest), where | is ...
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### How to find the factors of the modulus? [duplicate]

In the article "A Method for Obtaining Digital Signatures and Public-Key Cryptosystems", the original RSA article, it is mentioned that Miller has shown that n (the modulus) can be factored using any ...
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### RSA - Why should we sign hash rather than raw content? [duplicate]

Apart from obvious performance considerations, is there any mathematical or crypto reasons that imply that we sign a hash rather than a raw content ? I read that it was because the hash must fit in ...
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### Possible to know who is the owner of a message encrypted with RSA public key

Given the scenario in which I want to send 10 messages either to Stalio or Olio. I encrypt these messages with their respective public keys using textbook RSA, before sending the messages to their ...
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### Probability of factoring keys as a function of bit length [duplicate]

kinda new here, I had a question pertaining to someone being able to factor one's RSA keys through the GCD. Anyways the question goes that there are two people: A and B. A makes his/her private key as ...