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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271 views

Chain several RSA encryptions without increasing the message size

I would like to be able to encrypt the output of RSA with RSA again without having the output grow in size over time. In other words, I have some data $D_0$ which I want to encrypt with RSA: $D_1 = ...
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1answer
328 views

Cracking an RSA with no padding and very small e

I have a project wherein I have to crack a given cipher text encrypted using RSA and have been given N and e. Can someone suggest an RSA attack using a very small exponent e(here e=3) and no padding?
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1answer
288 views

Is it possible to determine the group order by knowing the “public” and “private” key exponents in an RSA group?

I have an RSA group with modulus $n = p \cdot q$, two safe primes $p=2p'+1$ and $q=2q'+1$ and the "public" and "private" key exponents $d$ and $e$. $\phi(n) = 4p'q'$ is the order of the RSA group. If ...
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1answer
385 views

Are RSA signatures deterministic?

If I sign the word HELLO with the mechanism "NONEwithRSA" with the same private key, do I always will have the same signature? A Java example always return ...
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2answers
266 views

Is semantic security important in a hybrid cryptosystem?

RSA doesn't provide semantic security when used unmodified, and neither does the commonly used PKCS#1 v.1.5 padding scheme for encryption. Is this a problem for hybrid cryptosystems at all? My ...
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1answer
322 views

Why is RSA usually limited to messages up to 1 block

I'm wondering why RSA encryption usually is only used for messages that fit into one block. For larger messages hybrid encryption in combination with symmetric ciphers like AES seem to be the solution ...
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1answer
915 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 ...
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3answers
475 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, ...
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1answer
142 views

Calculate the RSA private exponent from the CRT parameters

I am trying to make the RSA structure of Openssl manually, knowing the public key ($n$, $e$) and the CRT parameters $p$, $q$, $d_P$, $d_Q$, and $u = q^{-1} \mod p$. That is, I want to get the $d$ ...
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1answer
356 views

Precomputation attacks on RSA

Are precomputation attacks - such as outlined in RFC 3610 chapter 5 - possible on RSA PKCS#1 v1.5 signature generation? If yes, are such attacks taken into account when calculating the cryptographic ...
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2answers
359 views

RSA Key Generation Parameters - public exponent, certainty, string-to-key count

I want to know what values are appropriate for the public exponent and certainty when generating an RSA Key (for example using Bouncy Castle RSAKeyGenerationParameters function). What is the ...
2
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1answer
177 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. ...
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1answer
406 views

Attack of an RSA signature scheme using PKCS#1 v1.5 encryption padding

My best interpretation of this question is that Java's crypto API has been subverted to perform RSA signature using PKCS#1 v1.5 encryption padding. Assume the signature $S$ of a message $M$ is ...
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1answer
193 views

Why should a signature use PSS padding in RSA?

Suppose I send a message using AES (private keys already negotiated securely) and I send a hash of this message using RSA (encrypted with private key) with OAEP to verify the authenticity and ...
2
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1answer
191 views

RSA key length choice for TLS when confidentiality not important?

I've a couple of questions about this, the scenario is embedding a key pair in a hardware device which will speak with other hardware devices over tls. computing resources are an issue so i want to ...
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2answers
372 views

Computing p and q from private key

We are given n (public modulus) where n=pq and e (encryption exponent). Then I was able to crack the private key d, using Wieners attack. So now, I have (n,e,d). My question is, is there a way to ...
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1answer
349 views

Generate key pair deterministically from a particular seed [duplicate]

I've been reading "SQRL Secure QR Login" at Gibson's website, and I'm wondering if there is a way to generate an RSA private/public key-pair based on some cryptographically secure input, so that if ...
2
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1answer
623 views

CKM_RSA_PKCS vs CKM_RSA_X_509 mechanisms in PKCS#11

What is the exact difference between the CKM_RSA_PKCS and CKM_RSA_X_509 mechanisms in the PKCS#11 v2.20 specification (Please ...
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1answer
65 views

Comprehension question on a signature protocol based on the RSA assumption

We have the following two-party protocol between Alice and Bob. Alice sends messages $m_1, m_2, \ldots \in_R \mathbb{Z}_n^*$ to Bob and Bob signs these values by calculating $v_1, v_2, \ldots \in_R ...
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2answers
959 views

What data is saved in RSA private key?

What data is saved in RSA private key in openssl? How to view it? Wikpedia says these variables are saved.
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1answer
84 views

What is the most secure way to let Alice “input” her private key, transfer it to the server and decrypt the message?

What is the most secure way to let Alice "input" her private key, transfer it to the server and decrypt the message? (Then destroy the private key on the server) Every connection is using SSL. ...
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1answer
408 views

using Post-quantum asymmetric ciphers instead of RSA

We can't trust RSA to encrypt our Emails so what is best post-quantum cryptography system as alternative for RSA which provide good security and don't be breakable? because McEliece cryptosystem looks ...
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2answers
170 views

RSA keys finding when messages are known

I have this situation, where, in a game, people send messages to each other (game moves etc...) These messages need to be encrypted, and should only be readable by the destination person. I am using ...
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3answers
3k views

RSA Proof of Correctness

Can anyone provide an extended (and well explained) proof of correctness of the RSA Algorithm? And why is it needed? I can't say that this or this helped me much, I'd like a more detailed and newbie ...
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1answer
341 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 ...
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1answer
162 views

2048-bit RSA Decryption

Im in need of help with this study question. I heard that there was some relation between small a's and b's and being able to do a trick but I cant find where I read it in my book. Could someone help ...
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1answer
57 views

Recover plaintext in passive attack of RSA of coprime public key

I have a situation in RSA like this. Charles sends same message $m$ to Alice and Bob encrypted with $e_A$ and $e_B$ respectively. It happens that he they are under same modulus $n$ and $gcd(e_A, ...
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1answer
187 views

Small Encryption Exponent

I am trying to crack an unpadded RSA set up for a homework. I have public key (R,e) and encrypted message E. ...
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1answer
233 views

Can I remove new lines in a public key?

Can I remove new lines from the rsa public key file to get a one line string? So the question is if the key looks like this AAA BBB CCC or ...
2
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1answer
187 views

RSA Blind Signature Attack

In Information Security Class I learned a non-adaptive chosen ciphertext attack using "blinding" but I just can't follow the proof and therefore can't reconstruct it. From what I've found out, it ...
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2answers
1k views

The modulus of RSA public key

I am studying the RSA cryptosystem. The public key consists of $(n, e)$, the modulus (product of two large primes), and the encryption exponent. I want to separate the modulus $n$ and exponent $e$. A ...
2
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1answer
340 views

Montgomery Ladder vs Double-and-Add

I would like to know what (if any) are the advantages of using Montgomery Power ladder over the Double-and-Add-Always algorithm. I think that firstly, Monty would be slightly faster than DoubleAndAdd. ...
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4answers
666 views

Pseudocode for constant time modular exponentiation

I'm looking to implement modular exponentiation (for RSA) in constant time, but most of the examples I've found are more mathematical descriptions of the operations. Are there any references with ...
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3answers
527 views

How do institutions like banks do RSA with big primes?

When encrypting with RSA it is often infeasible to decrypt by just doing c^d mod n, because for example when using the primes $(p,q)=(12553,1233)$, which are small ...
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87 views

Usability of padding scheme in blinded RSA signature?

In Wikipedia's article on Blind signature, in the section Dangers of blind signing which describes RSA blinding attack one reads the following This attack works because in this blind signature ...
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1answer
998 views

Is it true for Java that the transformation mode and padding is ignored when using RSA?

Consider GregS's comment to this question (more specific to bouncycastle's provider implementation): http://stackoverflow.com/questions/11717646/bouncycastle-rsa-key-size-and-padding The mode, ...
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1answer
151 views

Good Encryption Exponent

I have placed a bet that I can create a public key such that my adversary will not be able to crack (decrypt) it for at least one week. For my primes $p$ and $q$, I chose very large numbers that are ...
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1answer
206 views

How vulnerable is RSA when using it to encode ~1000s of datasets with 500bytes each? How easy can the private key passphrase be hacked?

I know that this is not the best use case for RSA, but for a customer of mine I have to encode user data on the server in a way so that it can be decoded/downloaded by the customer through a "secure" ...
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1answer
98 views

Verifying a Signature

Alice publishes $(n,e)$ where $n$ is exponential modulus and $e$ is the public key. We have $n=80$ digit number and $e=3$. Bob, in correspondence with Alice, asked Alice to prove she is really Alice, ...
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1answer
361 views

Prime number theorem - RSA

I am having trouble understanding the prime number theorem. As part of some revision for an exam, I am trying to answer the following questions (but seeing as I don't understand the concept of the ...
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2answers
440 views

How can mega store my login details and still be secure?

I understand how Mega's encryption works. For a quick summary of all those in the future looking for an answer on this... here is how it works: Upon first signing up for an account you make a ...
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1answer
269 views

Is this method for exchanging private key using RSA sound?

Bob know's Alice's public key, and he wants to make sure he's connecting to the one which has that key. Furthermore, Alice wants to verify when she gets a connection from Bob who'll give his public ...
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1answer
89 views

Individual bits of Textbook RSA

This question relates to the underlying RSA assumption. Forgetting about the fact that Textbook RSA is deterministic, I am curious about the assumed strength of the RSA problem. Does RSA hide all ...
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6k views

Decrypt digital signature using RSA public key with openssl

I have a digital signature that was created using the following algorithm: a SHA-256 hash of the body of the message is calculated. It is then signed using an RSA private key and the result is ...
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2answers
344 views

Encryption with private key?

we normally always encrypt by public key and decrypt with private key. If i encrypt with private key, then its still secure as normal PKI ? i mean known-plain-text will not take private key on the ...
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2answers
177 views

Is there a way to compare the 923 bit pairing based key with RSA or AES, etc

I've see many articles, most of them basically the same, praising Fujitsu for cracking what is referred to as a 923 bit pairing based encryption. I understand that in comparing RSA to AES you've got ...
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1answer
145 views

Is there a way to provide 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 ...
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1answer
102 views

Is it possible to spoof an identity cert modulus?

I was looking at FOAF+SSL and wondering if its possible to spoof the modulus of the browser certificate so that the FOAF and browser certificate's modulus match?
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86 views

Implementation of garbled circuits using RSA

I was just reading these notes on garbled (Yao) circuits and I just stuck trying to figure out how an implementation of Table 1 would work using RSA encryption. In RSA the public key is (n,e). So for ...
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128 views

Generation of N bit prime numbers -> what is the actual range?

Short version: When generating a prime number of N bits, should I draw random numbers from the range $[0 , 2^n]$, or $[2^{(n-1)} , 2^n]$? Context: I'm trying to implement a toy-version of RSA as a ...