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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2
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2answers
196 views

At what stage is DHE and RSA used during the SSL/TLS handshake?

At what stage of the SSL/TLS handshake is the DHE and RSA used and what is the purpose of using a pre-master secret when you could just use RSA to exchange the symmetric key (i.e. AES) for further ...
0
votes
1answer
63 views

Is it secure to choose d in a RSA key pair?

An RSA key pair consists of the private key $(n,d)$ and a public key $(n,e)$ such that $de \equiv 1 \bmod{\lambda(n)} $. Usually one chooses a small $e$ and computes $d$ by inverting it modulo ...
0
votes
1answer
255 views

Verify Signature Failed [closed]

I am writing a small module which will verify signed message. Message will be signed using private key in Smart Card. The inputs are: Signed Message Original Message Public Key / Certificate with ...
-2
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1answer
324 views

Encrypting with private key in Public Key InfraStructure [closed]

In Public key infrastructure, the MD5 of a piece of data is encrypted with the private key of a sender and this encrypted MD5 – along with the data – is again encrypted using an algorithm like AES or ...
2
votes
1answer
211 views

Is it true that for RSA with no padding, the length of data must be equal to the length of key?

The question pertains not in terms of security but computing operational functionality, as it how the computation is done. Is it true that for RSA with no padding, the length of data must be equal to ...
5
votes
1answer
287 views

How are trapdoor functions developed/found and where can I find existing ones?

Trapdoor functions are a fundamental part of public key cryptography. An example of the most common trapdoor is Prime Factorization, used in cryptosystems such as RSA How are these trapdoor ...
3
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1answer
178 views

Is PKCS #1 v1.5 RSA encryption padding secure under these conditions?

The PKCS #1 v1.5 padding scheme for RSA has been proven to have some weakness when used with TLS for example. My question is: is it still secure under the following conditions? Alice sends a ...
1
vote
1answer
121 views

Non-interactive Zero-knowledge proof signature validation without public key

I'm looking for a method for a scenario with following requirements: At least 3 people (A,B,C,...) are in a Network where they can broadcast messages to everyone but not communicate with a specific ...
1
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0answers
71 views

RSA timing attack

Given an RSA implementation that uses Montgomery multiplications and CIOS exp algo, but NOT CRT. Given a decryption1 oracle that takes chosen cipher text and responds the plain text and the time it ...
0
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0answers
110 views

Is this a secure (and correct) sign-then-encrypt technique for transferring messages?

After reading some information on the way iMessage works I have been working on writing some code to try my hand at securely transferring messages in a similar manner and I wanted to confirm that the ...
1
vote
1answer
95 views

Difference between known-plaintext attack and forward search attack

I am looking at the different attacks on RSA. I came across known-plaintext attack where the public key can be used to encrypt all possible messages until it finds a match on the sent encrypted ...
3
votes
1answer
88 views

Should different key pairs be used for signing and encryption?

In the recent iOS Security white paper from Apple (February 2014), the section on iMessage discusses using two different asymmetric key types as part of its standard operation: When a user turns ...
4
votes
1answer
107 views

Difference RSA keypair creation openSSL and openPGP?

Creating a 2048bits RSA keypair I figured that doing this using openssl takes as an input 32bytes of "randomness" from /dev/urandom gpg (openGPG) takes as input ...
1
vote
2answers
469 views

RSA problem if i choose two specific small prime numbers?

I know that rsa normally is made to make it with big integers, but i trying to make the algorithm myself (with the help of wikipedia) and I´m making it with small numbers to track the problems easily. ...
-3
votes
1answer
49 views

Selection of cryptographic functions for OAEP

I can't understand how the "cryptographic functions" are to be selected RSA + OAEP which are used in OAEP. How to choose these "cryptographic functions"(G and H)?
2
votes
0answers
55 views

Timing attacks against RSA, DH and AES

I have been reading about “Timing Attacks on RSA: Revealing Your Secrets through the Fourth Dimension” by Wing H. Wong. I was wondering if this attack is feasible while signing with RSA and, if yes, ...
0
votes
0answers
71 views

Where can I download a database of RSA keys?

I'm looking to do some research into how RSA is used in the wild. I've read through a few papers and it seems other researchers have had no trouble collecting millions of keys to perform analysis on. ...
2
votes
2answers
508 views

How to calculate the maximum output size for data encrypted with a RSA Private Key?

I have an an encryption algorithm I am working with that looks like this: prv_key_enc(sha1_hash(data)) Where, the RSA parameters are: RSA/ECB/PKCS1Padding 1024 ...
1
vote
0answers
81 views

Is MITM possible after key exchange phase done successfully in RSA?

Is MITM attack theoretically possible after public/private key pair exchange is done successfully. Say Alice and Bob have genuine public keys of each other. Is MITM possible further during ...
1
vote
1answer
88 views

Can I use asymmetric encryption for more powerful write-protection?

I have a game that I am developing which uses a locally-stored internal database. It does not matter to me whether a user can read the file (which, to me, means I don't need a symmetric cipher), but I ...
3
votes
1answer
155 views

Questions about OAEP for RSA

I have two questions about OAEP for RSA. How are the number of bits to pad with 0 chosen? For example, if I'm sending a 255 byte message with RSA-2048 I have 8 unused bits (1 byte). Should I split ...
1
vote
1answer
133 views

Check the validity of a rsa key pair with only the public key? [duplicate]

I am currently developing a messaging application that uses rsa end to end encryption. The client generates permanent rsa keys, and sends the public key to my server for account management. As it ...
5
votes
2answers
1k views

How to calculate the time it'll take to crack RSA or DH?

Sometimes the easiest way to describe security of a type of cryptography is to say that "the time it takes to solve for an x-bit key would be y years". How would one go about doing such a calculation ...
6
votes
1answer
612 views

Why Elliptic curve cryptography are not popular in practice

RSA and ElGamal can be implemented using the technique of Elliptic curves. I am confused on why the it seems that Elliptic curves are not so popular in cryptographic applications since they provide ...
1
vote
4answers
243 views

Does it make sense to have a 4000 bit long key?

My question is about the key length of a asymetric algorithm. How is it possible to memorize or remember a key that is about 4000 bits long?
-3
votes
1answer
109 views

RSA public key security issue

The public key for RSA is $[e,n]$. Since $n = p * q$, are $p$ and $q$ already exposed because it takes no effort to figure out $p$ and $q$ from $n$?
4
votes
1answer
194 views

Timing Attack on RSA

So far I have researched on timing attack on RSA, We all know the ransomware named Cryptolocker it uses RSA 2048 bit encryption. Now is it possible to break the encryption using timing attack. I have ...
13
votes
8answers
2k views

RSA with small exponents?

Just to establish notation with respect to the RSA protocol, let $n = pq$ be the product of two large primes and let $e$ and $d$ be the public and private exponents, respectively ($e$ is the inverse ...
3
votes
0answers
100 views

How much plainext could be known without reducting security of RSA?

It is known, for example, that exposing 50% of most significant bits of RSA private exponent does not provide security risk (when a small public exponent it used). So how to qualify security ...
4
votes
2answers
944 views

Are there any standards of multi-prime RSA key generation?

FIPS 186-3 specifies a method to generate DSA parameters. Is there anything similar (official standard or widely-accepted recommendation) that shows how to generate the primes for multi-prime RSA?
1
vote
4answers
417 views

RSA with composite numbers

It has been said that RSA uses a modulus product of two prime numbers for security reasons. But does RSA even work correctly if we allow composite integers instead? I think that the answer is "NO". ...
3
votes
1answer
242 views

RSA with modulus product of many primes

I would like to ask what happens if we build an RSA system with modulus a product of more than 2 primes, for example let $n=p_{1}p_{2}...p_{L}$. I know only the classical RSA system with $n=pq$ with ...
9
votes
0answers
273 views

Who first published the interest of more than two prime factors in RSA?

Multi-prime RSA is now a well known technique: it uses $k>2$ distinct secret prime factors in the public RSA modulus, with the advantage that, using the CRT, we can gain a speed boost in ...
1
vote
1answer
91 views

Secrete message sharing using N private keys

I'm looking for an encryption scheme that could possibly meet the following requirements. Let, $X = plaintext$ $M = (pub, priv)$, where $priv == (Ky + Kz)$ Given ...
1
vote
1answer
70 views

Necessity of changing $p$ and $q$ when your private key is exposed?

Suppose your private key $d_1$ has been exposed. Instead of changing $p$ and $q$, instead you just choose a new public and private key (say $e_2$ and $d_2$) and use these instead. What kinds of ...
7
votes
3answers
2k views

Why hash or salt when signing?

I've seen an example of how to sign using RSA. Besides the signing itself (s = m^d mod n) it also hashes and adds an IV. Why is that needed?
0
votes
0answers
55 views

Plaintext patterns leaked based on single bit

Assuming that Elgamal is used as an encryption cipher, where lets say $p$ is 2048bit prime. Is it possible for an attacker to figure out $x$, a secret key, if any part of 2048 bits ciphertext and ...
2
votes
2answers
150 views

RSA: What happens to restrictions of plaintext n, dependent on p and q?

Ok - i will try to ask my question as clear as possible. Im getting a little deeper into the RSA-cryptosystem. At one point i'm a little confused. We have a plaintext $x$ and ciphertext $y$, with $x ...
11
votes
6answers
5k views

Is Diffie-Hellman mathematically the same as RSA?

Is the Diffie-Hellman key exchange the same as RSA? Diffie Hellman allows key exchange on a observed wire – but so can RSA. Alice and Bob want to exchange a key – Big brother is watching everything. ...
1
vote
1answer
152 views

Certificate signature with SHA-1 and RSA: where do 1888 bits come from?

Plenty of X.509 Certificates use "PKCS#1 SHA1 with RSA encryption" as the Certificate Signature Algorithm for generating a 2048-bit signature. The SHA-1 hash function generates a hash value of 160 ...
0
votes
0answers
74 views

how to calculate power $n$ over Gaussian integers?

In the paper Extended RSA cryptosystem and digital signature schemes in the domain of Gaussian integers the authors calculate $(4007621+145835\cdot i)^{7848211742013} \mod (x)$, please explain to me ...
1
vote
2answers
187 views

How can I simulate and measure brute force hacking using RSA?

I want to implement brute force hacking using RSA. How can I simulate and measure time duration? What software (or software-based simulator) would be needed?
5
votes
5answers
447 views

Is there a technique to confirm that a given large integer value is a product of two primes?

Given a list of 2048 bit integer values in which one or few 2048 bit integer values may be product of two prime numbers and other values may be just 2048 bit odd integers numbers. My question is - ...
1
vote
1answer
159 views

Short length asymmetric encryption?

I want to send out short messages to the world which listeners could verify to be send from me. The way this is usually done is to encrypt the message with a private key where the readers decrypt it ...
1
vote
2answers
260 views

Securely send public key from client to server in RSA?

I have a client and a server communicating with messages encrypted using RSA. Initially, the client knows server's public key, but the server does not know the client's public key. Is it possible to ...
6
votes
3answers
496 views

Initialize a PRNG with a password

Let's assume that we have a secure PRNG. Is it "safe" to initialize it with password, or seed based on a password like SHA256(password)? If yes, is it "safe" to generate an RSA or DSA key from it? ...
0
votes
2answers
140 views

Encryption of a number with RSA bigger than $n$

I'm having trouble understanding why encrypting a number $m$, which is larger than $n=p\cdot q$. I've looked into the following threads: Why RSA can't handle numbers above 76? Why does plain RSA ...
1
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2answers
92 views

Proof for exponentiation in modular arithemtic

If $e$ is a natural number, then this is true: $$m^e \bmod\ n = (m\bmod\ n)^e\bmod\ n$$ This is often used when encrypting, especially with RSA, since one can avoid directly calculating $m^e$, ...
2
votes
1answer
266 views

Why can ECC key sizes be smaller than RSA keys for similar security?

I understand how ECC is based on the discrete log problem and RSA on integer factorization. I've read several references that show how a solution to either of these problems can typically be adapted ...
1
vote
1answer
100 views

Usage of Fermat primes in RSA

Why are Fermat primes ($2^{2^n}+1$) useful as $e$ (the public key) in RSA encryption? I understand why $2^n+1$ primes are useful, because they would simply be ...