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.
1
vote
2answers
123 views
Idea for secure password hash-likes, is this feasible/usable/workable?
(Hand moved from stackoverflow.com,due to suggestion)
Since breaking password hashes has become a new passtime for scriptkiddies, I thought of the problem and came up with a novel(?) idea.
store ...
0
votes
0answers
121 views
RSA SecurID: Unable to access via web manager [closed]
I'm having an error with access to the web admin of my RSA SecurID server.
I'm getting an error of 100: access denied. The RSA ACE/Server rejected the passcode.
I'm guessing that this is most likely ...
2
votes
2answers
192 views
Is RSA in a ECB-like-mode safe for bulk encryption?
Let's say I would like to communicate with my friend using asymmetric/public-key encryption, e.g. RSA.
(Note: I do realize that in practice this is done through an intermediate symmetric key, but ...
1
vote
1answer
181 views
“Signing” with public key
For this question, the following caveats and assumptions hold:
There exists a 2048-bit RSA key pair used exclusively for signing/verification
The private key is kept completely private
There exists ...
1
vote
2answers
99 views
When to prefer exchanging cryptographic certificates over exchanging only public keys?
Let's think of the following case:
A group of peers want to exchange messages with each other. They use public-key cryptography to sign and encrypt messages. Anyone with any name can join the ...
3
votes
1answer
124 views
Safely use CryptSignAndEncryptMessage?
I am developing an application that sends messages which I want to encrypt and sign. The CryptoApi offers a function called CryptSignAndEncryptMessage.
The description says, what this function ...
3
votes
2answers
466 views
Difficulty of breaking RSA for a given key size
Is it true that breaking a 1024-bit RSA key is as difficult as breaking a 128 bit symmetric key (e.g. AES)? I know that breaking a RSA key is equivalent to factoring the modulus $N$. To factor it, you ...
5
votes
1answer
833 views
Chinese Remainder Theorem and RSA
Wikipedia has a nice section regarding the speedup of the RSA decryption using the Chinese Remainder Theorem here. I need to understand the implementation of a similar speedup for the encryption ...
5
votes
1answer
279 views
Are there any MGF1 and OS2IP functions available in C?
I need MGF1 and OS2IP functions, as defined in the PKCS #1 v2.1: RSA Cryptography Standard.
Is there anything available in OpenSSL, or any other open C library?
1
vote
2answers
544 views
Why DSA cannot be used for encryption?
Here it is mentioned that DSA cannot be used for encrypt. But Both RSA and DSA can be used to generate public and private keys, right? (Or am I wrong?). Then why can't I use the DSA public key to ...
-1
votes
1answer
107 views
How can we find Public key have only 8 or 16bits? How many messages does Eve need to know the Public key in RSA?
Suppose Alice sends messages to Bob by encrypting the messages with Bob's public key.
Eve knows that the data is encrypted using RSA, but does not know the public key. Can Eve figure out the public ...
2
votes
2answers
266 views
Is it possible to figure out the public key from encrypted text?
Suppose Alice sends messages to Bob by encrypting the messages with Bob's public key.
Eve knows that the data is encrypted using RSA, but does not know the public key. Can Eve figure out the public ...
2
votes
0answers
113 views
RSA reencryption scheme
Is there such an algorithm that would allow to upgrade the encryption of a RSA-encrypted message without revealing the plaintext to the untrusted user?
Basically, such an algorithm would probably be ...
2
votes
1answer
293 views
How many RSA keys before a collision?
I was wondering how many possibilities of private/public keys there are? If a million people for whatever reason tried to generate 5keys each in the same minute (on the same date and time) is there a ...
1
vote
3answers
301 views
RSA finding the inverse of the public exponent
I have a very basic doubt in RSA key generation and its usage.
In RSA key generation you choose two large prime numbers of a very large order. Then you multiply them.(eq $p \cdot q = N$) Now, ...
6
votes
3answers
359 views
Security equivalence proofs for breaking RSA
It is my understanding that while a practical solution to the factoring problem will definitely break RSA, it has never been proven that the security of RSA is equivalent to factoring.
In otherwords, ...
3
votes
3answers
469 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?
2
votes
1answer
430 views
How to sign a message using RSA?
Assuming I already have a D, P, Q, etc of an RSA key: How do I now sign a message? If it matters – the message is around 100 bits.
I don't know much about cryptography, but I can get these numbers ...
1
vote
1answer
136 views
How are the primes used to generate RSA keys?
I am confused about how keys in RSA asymmetric encryption are generated and what the implications for open communications are. Textbooks say the one-way function is merely two primes (with some ...
3
votes
2answers
289 views
Can RSA encryption produce collisions?
In RSA, a message is encrypted by $m^e \pmod N$. $N$ is the modulus, $m$ is the message and $e$ is the public exponent. (I know that $m$ should not be greater than $N$.)
My question is, can $m^e$ be ...
5
votes
1answer
348 views
Would RSA-encrypting a private key for itself constitute a vulnerability?
I'm planning to encrypt some individual files for storage, using the GnuPG implementation of RSA. If I happened to encrypt the private key corresponding to the public key used for encrypting -- either ...
1
vote
2answers
175 views
One-way function and factoring
I am confused about the hardness of the one-way function behind cryptography -- if someone could factor the large number produced back into two primes quickly then the one-way function would be ...
2
votes
2answers
2k views
How does a chosen plaintext attack on RSA work?
How can one run a chosen plaintext attack on RSA?
If I can send some plaintexts and get the ciphertexts, how can I find a relation between them which helps me to crack another ciphertext?
1
vote
2answers
216 views
My custom handshake
I am a beginner in cryptography and I designed a custom handshake between 2 entities $\rm C$ (client) and $\rm S$ (server) which should meet the following requirements:
Requirements:
The handshake ...
4
votes
1answer
115 views
In RSA, rationale for prime $p$ with $p-1$ having prime factor $u$ with $u-1$ having large prime factor?
In the 1978 RSA paper, it is recommended, among other things, to choose primes $p$ such that $(p-1)$ has a large prime factor $u$. This was motivated by Pollard's p-1 algorithm. Further, the authors ...
5
votes
3answers
428 views
Is RSA padding needed for single recipient, one-time, unique random message?
I want a way to encrypt files using this process: http://crypto.stackexchange.com/a/15 . That is: generate a random password, use that to AES-encrypt a file, and use an RSA public key to encrypt the ...
3
votes
3answers
4k views
RSA encryption with private key and decryption with a public key
Does the encryption with a private key and decryption with a public key works in RSA? Is it done when we use RSA for sender authentication ?
Thanks.
4
votes
1answer
185 views
Why does RSA give better security on longer messages?
I am trying to understand the notion of RSA security.
Choosing a public exponent where $e = 3$ facilitates the calculations, considering that it is secure if the plaintext or message is long.
If the ...
8
votes
4answers
642 views
Does RSA work for any message M?
I decided to read the original RSA paper A Method for Obtaining Digital Signatures and Public-Key Cryptosystem because of a question I had about RSA (which is not the question I'm about to ask, but ...
3
votes
2answers
1k views
Difference between “Signature Algorithm” and “Signature Hash Algorithm” in X.509
What's the difference between the "Signature Algorithm" and the "Signature Hash Algorithm" found in an X.509 certificate? Why does it need a "Signature Hash Algorithm"?
Edit:
I'm creating the ...
4
votes
2answers
203 views
X.509 CSR: Why does CA remove signature?
I just read this article on Wikipedia: Certificate Signing Request
I'm not a PKI or Crypto expert. As I understand, a CSR (certification request) is always signed by the PKCS#10-Request creator.
...
2
votes
1answer
125 views
RSA-OAEP versus RSA with Fujisaki-Okamoto construction
I was wondering why the Fujisaki-Okamoto construction (or one of its variants) is not (at least commonly) used with RSA to achieve CCA2 security? Does anyone know of any speed comparisons between RSA ...
7
votes
7answers
3k 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.
...
4
votes
0answers
78 views
RSA security assumptions - does breaking the DLP also break RSA? [duplicate]
Possible Duplicate:
Would the ability to efficiently find Discrete Logs have any impact on the security of RSA?
I'm wondering if breaking the DLP, that is the basis for ElGamal and DSA, ...
2
votes
1answer
111 views
Signing a GCM MAC
If I encrypt a message with AES-GCM, is it safe to use the MAC as the hash in a DSA/RSA signature? That is, if someone knows the AES key and nonce, will they be able to generate a different message ...
4
votes
1answer
199 views
Threshold Signatures for RSA and DSA
I have a few questions relating to threshold signatures: a scheme where $n$ participants hold a key share and any $t$ of them can conduct a protocol using their shares that results in a valid RSA or ...
6
votes
1answer
300 views
Exposing RSA private-key data… bad?
We know that exposing $p$, or $q$ or $\phi(n)$ results in trivial attacks on RSA since they allow us to factor $n$ and to compute the private exponent $d$.
In OpenSSL (and most RSA implementations) ...
1
vote
1answer
98 views
Proof of batch RSA security
Suppose we have two encrypted messages with two different public key issued from the one server. There is a client who wants to send these to messages to the server.
In the middle there is an ...
4
votes
2answers
297 views
Does RSA padding have to be unpredictable if the payload is?
I'm trying to understand the precise requirements on padding when using RSA for encryption.
Suppose Alice uses RSA to encrypt a payload $M$ that cannot be guessed (say, a random nonce): Alice send ...
4
votes
1answer
181 views
Anonymous trust/reputation system
Suppose there are 3 persons, Alice, Bob and Peter.
They are identified by their pseudonyms (public RSA keys).
Alice has a key Alice, Bob has ...
4
votes
1answer
463 views
How to better generate large primes: sieving and then random picking or random picking and then checking?
I'm writing an RSA algorithm, and am wondering what is the best and/or usual way to choose the initial prime numbers (p and q).
I know of two methods to achieve this, one based on a prime number ...
6
votes
3answers
1k views
Why RSA encryption key is based on modulo(phi(n)) rather than modulo n
While calculating RSA encryption key we take modulo(phi(n)) rather that modulo(n). I couldn't understand why its so?
2
votes
1answer
409 views
Is RSA of a random nonce with no padding safe?
Consider the following protocol: Bob has a private RSA key $B_{priv}$, and Alice knows the public key $B_{pub}$. Alice wants to send confidential messages to Bob (no integrity intended). To send a ...
6
votes
2answers
539 views
How much can we compress RSA public keys?
I am wondering to what degree we can define an RSA variant, with a security argument that it is as safe as regular RSA with a given modulus size $m$ (e.g. $m=2048$), in which the public key has a ...
3
votes
3answers
302 views
How can I avoid calculating with huge numbers when implementing the RSA algorithm
There is 26-letter English alphabet.
There is the plain text: TRYAGAINLATER.
I need to encrypt it by RSA algorithm with the public key 53.
What is the ciphertext?
...
6
votes
1answer
641 views
Why does the PKCS1 RSA private key structure contain more than just exponent and modulus?
The ASN.1 spec for the PKCS1 RSA private key format is as follows:
...
1
vote
1answer
2k views
Calculating private keys in the RSA cryptosystem
The number $43733$ was chosen as base for an implementation of the RSA system.
$M=19985$ is the message, that was encrypted with help of a public key $K=53$.
What is the plaintext text?
What is the ...
3
votes
2answers
3k views
When to use RSA and when ElGamal asymmetric encryption
If i am not wrong in cryptography there are 2 basic cryptographic schemes for public key cryptography. RSA encryption whose security is based on the infeasibility of solving the factoring of big ...
5
votes
3answers
591 views
Is it possible to validate a Public Key in RSA?
If I have a 1024-bit number, and someone is telling me that it is in fact a valid RSA public key, is there any way I can quickly validate that it is indeed so (without cracking RSA)?
(I suppose I am ...
1
vote
0answers
76 views
Two untrusted party want to exchange data: how to ensure each one gets the data it needs? [duplicate]
Possible Duplicate:
Two untrusted party want to exchange data: how to insure each one gets the data it needs?
I am trying to come up with what could maybe be a novel algorithm for an ...
