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.

learn more… | top users | synonyms

-1
votes
1answer
106 views

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 ...
0
votes
1answer
100 views

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 ...
3
votes
1answer
102 views

Space needed to store an RSA private key

How much space is actually needed to store a $4096$-bit RSA private key? I originally assumed $0.512$ kB since $\frac{4096}{8} = 512$, but then I started to wonder whether it was in hex. Simply, ...
1
vote
0answers
21 views

Should we use exponent 3 in RSA-OAEP?

As I understand it the proof that RSA-OAEP is secure in the random oracle model is much tighter for exponent 3. Does that mean that exponent 3 should be chosen?
0
votes
1answer
81 views

One-time pad using RSA and Diffie-Hellman functions

Suppose that Alice and Bob use an encryption algorithm based on a one-way function $F$ (Eve knows it), and $r$, a secret key shared between Alice and Bob (Eve doesn't know it). Key is computed as: $K ...
0
votes
1answer
73 views

Clifford Cocks Interview: “Raising numbers to a power with the product as modulus”

Disclaimer: I'm new to cryptography Background: Clifford Cocks, the former GCHQ mathemetician and crytologist, gave an interview where he said: "My thinking was that you need something that is ...
0
votes
1answer
106 views

How many bits of symmetric security does RSA-3072 actually provide? [duplicate]

I know that the sizes are standardized to $1024$, $2048$ etc. but they actually provide different security than $128$, $256$... for example $\texttt{RSA-}2048$ is actually $112$ bits of security and ...
0
votes
1answer
52 views

Is webkey a reasonably secure authentication system?

I just created Webkey in the last couple days. This should allow any website to do single-password auth with a much higher level of auth security and convenience for users (single password with ...
0
votes
2answers
127 views

How does SSL work on the browser

I recently bought an SSL certificate from a website and was able to make it work on my Apache server. As far as I know, it uses asymmetric keys and the private key is stored on the server while the ...
4
votes
1answer
329 views

For RSA keys, is the safety of a given key-length different for signing vs encryption?

I'm wondering if considerations of key-length are different when thinking about signing vs encryption. If for some reason, it was safter to use smaller keys for signing that would be interesting.
0
votes
1answer
17 views

CCA on PKCS#5 using error feedback

My question is about attacking PKCS#5 with CCA using the error feedback. What we learnt in class about PKCS#5: CBC requires padding to whole block boundary PKCS#5: standard padding If ...
0
votes
1answer
56 views

Storing RSA private key

Currently I'm developing an application where users generate their own pair RSA keys in order to achieve a secure communication with my server. Also clients are able to communicate directly, sending ...
0
votes
2answers
68 views

In case M is small is it possible to recover the message

In the plain RSA encryption, suppose $N$ is 1024 bits and the public key $e = 17$. Is it secure to use this setting to encrypt very small message, say $3 \leq m \leq 9$? In other words, is it possible ...
-1
votes
1answer
106 views

Speed of a 16384-bit RSA key

I don't think it makes much sense to use RSA keys to authenticate the establishment of symmetric keys with strengths less than their own. From what I know, a 16384-bit RSA key's strength is roughly ...
2
votes
0answers
63 views

Bitwise method of generating r for RSA-KEM

It seems that RSA-KEM has a very troublesome method of generating the secret $r$. It seems that the random value needs to be in the range $0 \le r \le {n - 1}$. Now most cryptographic environments ...
3
votes
1answer
90 views

Why is padded RSA not CCA-secure?

Why is the padded RSA construction given in the picture not CCA secure?
4
votes
1answer
94 views

Exposed raw RSA private key operation

Assume that there is a smartcard or other hardware token that exposes the raw RSA private key operation (modular exponentiation, with or without CRT parameters). Is there any possibility that raw RSA ...
1
vote
1answer
19 views

Will changing the RSA Padding in OpenSSL cause issues?

I'm currently looking at changing the padding type from one of the Oracle Padding attacks to a secure one. Would this break data already encrypted using the old method?
3
votes
1answer
74 views

Is RSA encryption without padding secure with NIST Key Establishment schemes?

NIST SP800-56B standard (addressing IFC-based Key Establishment schemes) defines some key establishment (KE) schemes using the RSASVE primitive in which the common secret $Z$ is encrypted with RSA-EP ...
0
votes
0answers
40 views

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 ...
3
votes
2answers
304 views

RSA: Recover e given factorization of N and plaintext/ciphertext pair

Is there a way to recover the public exponent e (assume in this case it is in fact not public) used in an encryption if I know the following: Factorization of ...
0
votes
2answers
115 views

Algebraic structures in RSA

Why do we need a field for RSA and what are the two operations in this field? Why can't we have a ring or group for example? Because in a group you also have inverse elements.
-1
votes
1answer
46 views

What's the best way to pad a message?

Currently my padding is adding a string of random characters $ l(N)/3 - (l(M) + 1) $ Long and just adding it to the messages, is this sufficient? $l(x)$ = length of a variable
-1
votes
2answers
53 views

Finding d given everything else in RSA [duplicate]

I've got everything else (e, p, q, phi(n), n), but cannot see a way to figure out what d should be. P and q are both 300 digits, so phi(n) and n are about 600 digits, but e is only 5 digits. I do ...
5
votes
2answers
104 views

Signing MD5 hashes with RSA? [duplicate]

Lets say I need to update a project and allow anyone to distribute the updates, however I need it to be secure, so I hash the data and sign the hash, this project uses MD5. How likely would it be ...
0
votes
1answer
50 views

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 ...
3
votes
2answers
195 views

Finding Private key in RSA with public key, cipher text and plain text

Is there a known 'non-brute force' method of determining a private key in an RSA system when all other parameters are know? I found the values of a ciphertext ($C$), its corresponding plaintext ($P$) ...
3
votes
1answer
52 views

Selective and existential unforgability of signature schemes

I understand that one can define EUF-CMA of a signature scheme is terms of a game where the adversary is allowed to query signatures on messages of his choosing, and at the end of the game he must ...
5
votes
1answer
143 views

What are the minimum constraints on RSA parameters and why?

The RSA cryptosystem only works if certain constraints are applied to its input parameters. Some of those constraints are made to make it "hard" to determine the private key whereas other constraints ...
3
votes
1answer
102 views

Anonymity problem after voting with blind signatures

In a distributed voting system (all the messages are public, but signed and maybe encrypted/blinded), having: $d$, $e$, $N$ — registrar key params $m$ — msg $r$ — random blinding factor $m'$ ...
1
vote
0answers
72 views

“Prime conspiracy”'s effect on cryptography [duplicate]

Recent news reported about the discovery of a "Prime Conspiracy" which can be read about here. In summary, researchers have discovered that the last digit of prime numbers have a greater ...
2
votes
1answer
89 views

Is there an asymmetric algorithm that can perform double encryption?

I'm looking for any asymmetric algorithm can perform the serial encryption, by serial I mean double or more encryption with different key(same key size). RSA can not do it since the cipher of the ...
3
votes
2answers
136 views

Why do we need Euler's totient function $\varphi(N)$ in RSA?

After we calculated $N = p * q$, we calculate $\varphi(N)$ and use it later to determine $e$ (PR) and $d$ (PU). But why? For decryption and encryption we only use $N$ and don't need $\varphi(N)$. So ...
3
votes
1answer
127 views

How do I attack an RSA setup where e is even?

As a challenge, we were shown an RSA setup where we have a big $n$ (617 decimal digits), $e=4$, and asked to recover three messages. (However, the messages are padded to the same length as the key ...
1
vote
0answers
54 views

Encryption & decryption of integers using modular multiplicative inverse and extended euclidean algorithm

I'm looking for a neat algorithm, which is capable of encrypting an integer to another integer and decrypting it again AND is secure. When I was in university, my professor showed me an awesome way ...
8
votes
1answer
404 views

Given enough RSA signature values, is it possible to determine the public key value?

Given enough RSA signature values, is it possible to determine which public key is required to verify the values? Could there be enough information to establish which key is required? Is there ...
7
votes
2answers
413 views

Given enough RSA ciphertext, is it possible to determine which key was used?

Given enough RSA ciphertext, is it possible to determine which public key was used to generate the ciphertext? Presume an unknown public key that was used to generate RSA ciphertext, and we have ...
3
votes
1answer
39 views

how is the rsa $publickey(n ,e)$ transformed into a textfile allowing its public distribtution?

wikipedia says about the keys itself: The public key consists of the modulus n and the public (or encryption) exponent e. The private key consists of the modulus n and the private (or ...
4
votes
1answer
33 views

Is it okay to use a variable-time RSA implementation to verify TLS certificates?

RSA as implemented by OpenSSL et al. needs to protect against side channel attacks, at a big performance penalty. However, TLS certificate validation involves no secrets. Therefore, I should be able ...
2
votes
2answers
101 views

Implementing RSA with small integers in CUDA

I have found some researches dedicated for speeding-up RSA calculations using CUDA. But I am wondering how they do that, given that the biggest unsigned int that could be declared in CUDA is 64 bit. ...
-3
votes
1answer
51 views

How does the math part of RSA work? [duplicate]

I understand the theoretical part of RSA (the concept of public and private keys), but I don't understand the mathematical part. Can anyone please explain it to me in simple terms? Thanks.
0
votes
1answer
168 views

Cube-Root attack - RSA with low exponent

I have this RSA public key ...
1
vote
1answer
87 views

Really simple RSA style public private key generator

I am giving a talk to high school students and would love to do a real life encryption/decryption demonstration. I am not too familiar with the maths but is it possible to create like a 5-10 bit ...
0
votes
1answer
50 views

Is sharing the RSA public key secure?

I am trying to understand how RSA public key cryptography works. I have the following questions: Are any attacks / compromises possible if a server sends its public key $(n,e)$ in the clear to a ...
3
votes
0answers
69 views

How common are weak RSA keys?

There exist certain attacks that can be used against RSA keys whose prime factors are of specific forms, such as one by Coppersmith. How common are these RSA keys? If you generate primes randomly, ...
1
vote
1answer
90 views

What is the importance of 1 < d < φ(n) and 0 ≤ m < n in RSA?

I'm a first year Maths undergraduate and we have recently gone onto RSA. I understand the majority of the algorithm using Fermat's Theorem etc. From the algorithm stated on Wikipedia: 4) Choose ...
0
votes
3answers
133 views

Does RSA have two trapdoors?

I watched some videos from Khan Academy explaining the algorithm for RSA encryption/decryption. They explained that there are two trapdoors, modular exponentiation being one and prime factorization ...
38
votes
6answers
219 views

How to check that you got the right key when brute forcing an encryption?

How do you know when you have the right key when brute-forcing? Let's say that they test the right key. They then have to check that the decrypted text makes sense. To do so, they can test whether ...
0
votes
1answer
72 views

How to decrypt RSA if ciphertext is less than the modulus and e=3?

I'm given a public key. Using openssl rsa ..... I got the public key has the exponent as 3. When I calculated the size of the ciphertext, it is 8 bits smaller than the 2048-bit modulus. How can I ...
3
votes
2answers
276 views

Is there any reason to use RSA or DSA when we have ECC?

I am having trouble coming up with a use case for RSA or DSA. It appears that ECC is better in every way. Is this true? I am looking for cases where RSA/DSA is superior to ECC, not where it is used ...