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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Storing AES encrypted RSA private keys on a server

I'm thinking about creating an encrypted messaging web application where users create RSA key pairs, they store the public key on the server for others to see and also store an AES encrypted private ...
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44 views

Franklin-Reiter related message attack m2 = a(m1)+b

As shown in their paper, https://www.cs.unc.edu/~reiter/papers/1996/Eurocrypt.pdf, if one is given an equation relating the two messages m1 and m2 as well as other information one can crack both the ...
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80 views

Is a RSA 2048 bits public key secure [duplicate]

I realize servers such as Google, Yahoo, which use RSA has 2048 bits public key. After comparing those keys, I realize that the public keys share a common property, that is first 9 bytes and last 5 ...
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56 views

Can public key be recovered from chipher text & encrypted private key?

I'd like to implement something like a write-once public/private encrypted shared secret (no better quick description for the lack of terminology knowledge). I guess, i'm trying to implement HSM. The ...
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35 views

Low exponent attack against RSA

According to this: http://www.cims.nyu.edu/~regev/teaching/lattices_fall_2004/ln/rsa.pdf One can calculate the message m, if there was no padding scheme involved. My question: is it possible to find ...
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61 views

rsa public and private keys

I have a question about RSA key generation: this is a simple rsa algorithm: Choose p = 3 and q = 11 Compute n = p * q = 3 * 11 = 33 Compute ?(n) = (p - 1) * (q - 1) = 2 * 10 = 20 Choose e such that 1 ...
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68 views

Montgomery Multiplication in FPGA explanation

I'm trying to implement an RSA module in a FPGA. I choose to use Montgomery multiplication. I've found a document where the Montgomery Multiplication is pretty clear. I don't understand only a step. ...
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134 views

Implementing a web app where the server cannot decrypt its own data?

I'm a cryptography novice, but I think that the world needs to move towards an "encrypt everything" mentality as much as possible. As a result, I've been thinking a lot about ways to build a web app ...
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93 views

RSA and ECDSA Certificate Sizes

Is there a table (or a whitepaper from official sources) that compares the size of X509 certificates generated with RSA (starting from 1024 bits) and ECDSA (starting from 160 bits) ? Thanks for the ...
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71 views

RSA: Common modulus attack problem [duplicate]

I understand in theory how the common modulus attack works (as described here: how to use common modulus attack?) Though, I did not understand completely how it worked with a negative $s_i$. Since ...
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146 views

RSA, finding p,q [duplicate]

If the public key $(e,n)$ and the private key $(d,n)$ are known, what is the easiest way to find the primes $p$ and $q$? When $n$ and $\phi(n)$ are given this is easy to solve. But I can't manage it ...
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73 views

Cryptodefense ransom use RSA-2048. Any chance with known plaintext attack? [duplicate]

The "new" kind of ransomware invade your computer and crypt all your files using the RSA-2048. Personally, I have been victim of cryptodefense: 40000 files encrypted... I'm not going to pay anything ...
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39 views

Does RSA work properly with non prime factors? [duplicate]

I know RSA should not use non prime factors for p and q for security reasons, but still, just out of curiosity, will RSA work 100% accurately i.e. message encrypted with one of the key produces same ...
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111 views

m ∈ Zn \Z*n, RSA works but not secure

If you happen happen to have a message m ∈ Zn \ Z*n, RSA works but not secure. How likely is it going to happen? |n|=1024 bits |p| = 512 bits |q| = 512 bits.
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60 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 ...
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164 views

How to safely sign a 6 characters String?

I have to decide, whether a document, which I am given, was correctly signed by a private key. my Ideas is to sign the document id using RSA with the private key and to print the following onto the ...
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111 views

RSA vs El Gamal digital signature. Which is more secure? [duplicate]

I'm reading about the notions of security concerning digital signatures and I can't understand whether RSA is more secure than El Gamal digital signature. Well, they are both prone to forgery, but I ...
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1answer
78 views

How to keep phi(n) secret in RSA?

As we know, RSA cryptosystem have both private key(a,p,q) and public key(b,n), by chinese remainder theorem and fermat's little theorem, we know that the importance of keep p and q secret, and from ...
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1answer
94 views

modulus condition [closed]

In RSA algorithm, the modulus $n$ should be chosen based on the below condition $2^{8(k-1)} \leqslant n < 2^{8k}$ Where $k$ is the byte length of the modulus $n$. for this condition I want the ...
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1answer
190 views

What length should the padding be when encrypting or signing with RSA?

I am wondering what length the padding should be when encrypting or signing with RSA. Does it matter what length the padding is, and if so — what length should it be? Another point: Should it be ...
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1answer
60 views

Textbook RSA with exponent e=3 [duplicate]

I remember $e=3$ is a bad choice for textbook RSA. But I can't really recall why. What happens if I choose $e=3$? Can I retrieve the message by simply calculating $\sqrt[3]{c}$? Why can't I do that ...
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1answer
199 views

Is it possible to find plaintext from ciphertext if (n) and (a) are known for RSA?

I have a couple of questions pertaining to a RSA problem. I need to decipher some ciphertext and find out what the original plaintext was. Modulus: $n = 2537$ and exponent: $a = 11$ Encrypting ...
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1answer
98 views

How to calculate bit strength of Integer Factorization Cryptography (IFC) such as RSA using Python

I would like to know how to calculate the bit-strength of Integer Factorization Cryptography (IFC) such as RSA by using Python. I gathered it is based off the complexity of factorizing the modulus ...
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49 views

The improvement of the private key exponent in the M.Weiner Attack

I am working on attacks on RSA and came across the M. Weiner attack. The limit for $d$ in order for the attack to apply is $d <= (\frac{1}{3})N^{0.25}$. The paper states that Boneh and Durfee ...
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82 views

Assuming that we had a way of finding primes, could RSA be used without computers?

I once asked a question "Would RSA make sense if we used no computers?". The answer was negative, because finding primes that would make secure keys would prove too hard. Assuming that we had found ...
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1answer
357 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 ...
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1answer
174 views

RSA given q, p and e?

I am given the q, p, and e values for an RSA key, along with an encrypted message. Here are ...
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1answer
56 views

How small are we talking about when defining the small public/private key exponent [duplicate]

I've been wondering about the 'small' part of the attacks on RSA, like the small public key exponent and the small private key exponent and what's not really clear is how small are we talking about? ...
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1answer
420 views

why RSA uses Semiprime numbers? [duplicate]

Why does RSA use semiprime numbers? Why not just use any big number ?? What is the advantage of the two original numbers being prime? Because factoring any big number will be difficult
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104 views

Can someone explain how this unpadded RSA formula works?

Taken from http://en.wikipedia.org/wiki/Homomorphic_encryption, $\mathcal{E}(x_1) \cdot \mathcal{E}(x_2) = x_1^e x_2^e$ $\bmod\; m = (x_1x_2)^e \;$ $\bmod\; m = \mathcal{E}(x_1 \cdot x_2)$ What is ...
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2answers
322 views

Is triple des similiar to RSA in that they message size is limited to the key size?

Is triple des similiar to rsa in that the message size you can encrypt is limited (unlike AES)? Yes you can break the message size into parts and apply it, but I'm not interested in doing that so I ...
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68 views

Cracking plain RSA by factoring the modulus n

This is the setup: I have both public and private keys of one "instance" of RSA. And I have only the public key of another RSA cryptosystem, but this system has the same modulus as the first one. I ...
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67 views

RSA-Like encryption for embedded systems [on hold]

I have been asked to study an encryption/decryption scheme in embedded systems, In the first figure you can see the process. I can't really seem to understand the process, its vulnerability, or find ...
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3answers
1k views

How can I find the prime numbers used in RSA?

I got this question in a local hacking event, but I couldn't solve it. Problem Statement ---- Continuing their snooping habit, NSA kept bugging Alice's communication. Resorting to the age old ...
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1answer
56 views

moduli in SSL certificates [closed]

this is normally seen in a typical SSL certificate. For the modulus, I know that it is represented in hexadecimal form, but why is there a semicolon (:) after every group of 2 digits? ...
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1answer
51 views

How to write the encrypted message after using RSA

I have created a RSA encryption/decryption program but how do i write out the results after doing a encryption? Right now I have it so that it will just print out the decimal value of one character ...
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1answer
109 views

What parts of number theory does the RSA algorithm use?

It is said that the RSA algorithm uses number theory. What parts of number theory does it use? I know it uses modular arithmetic and Euler's totient theorem and function. Is that all?
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1answer
391 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 ...
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1answer
207 views

Security of RSA-substitution-RSA

Following on from here, I am unconvinced that encrypting twice with RSA is a waste of time: doesn't it depend on what is placed in-between the two encryptions?. What would happen if a permutation was ...
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0answers
27 views

Real life RSA/El Gamal examples

Can someone direct me to examples of El Gamal and RSA that would be similar to real life (i.e. large primes). I wrote a code for encryption and decryption, but I wanted to test it against some larger ...
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0answers
1k views

encryption and decryption time for RSA-crt in java? [duplicate]

I try compute execution time for encrypt and decrypt data has 1024 bit = 128 byte in RSA-crt algorithm. I need this results. But I believe this result wrong. because big diffrent between execution ...
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1answer
114 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 $n$?
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1answer
1k views

Is it possible to generate an RSA SHA1 signature only from a public key?

Is it possible to generate signature only from Public key. See example below where i have valid signature but what if I change hash ? Is then any way to do this? Public key(160 bytes): ...
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1answer
54 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)?
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1answer
136 views

Currently i am doing decryption for RSA encoding and i face some problem with it [closed]

I am very new to cryptography so I don’t know much about it. I have been given a very large $N$ value and $E$ value to decrypt a ciphertext which was created using a AES 128 key and a IV by using RSA ...
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1answer
86 views

RSA Key and RSA Security

Is there any relationship between the RSA keypair standard and RSA security? Keypair: http://en.wikipedia.org/wiki/RSA_(cryptosystem) Security: http://en.wikipedia.org/wiki/RSA_Security If not, ...