An asymmetric cipher is an encryption scheme using a pair of keys, one to encrypt and a second to decrypt a message. A special class of asymmetric ciphers are public-key ciphers, in which the encrypting key need not be kept secret to ensure a private communication.

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can permutation matrix be found in parallel processing technique?

Let us say there exists a permutation matrix $n \times n$ for some large $n$. Then, there are $n!$ possible permutations. If one to use brute-force to find the secret permutation among $n!$ ...
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Best Asymmetric Encryption Standard for Communications? [closed]

I'm new to the standards of encryption. I understand the math behind RSA really well. I'm wanting to design an application for private peer to peer communications using RSA and wanted to know what ...
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78 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 ...
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1answer
64 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 ...
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112 views

Why is ElGamalEngine in bouncy castle restricting input data to be less than the length of the group parameter p?

I am currently using the ElGamalEngine of bouncy castle to implement exponential ElGamal for the purpose of making ElGamal additively homomorphic. To do this i raise the message to be encrypted to the ...
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2answers
141 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 ...
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1answer
44 views

Ensuring that an operation takes a relatively specific amount of time, but easily verify the result

I want an algorithm of some sort that can ensure that an operation takes a fairly specific amount of time, but proof that this operation was done can be completed relatively inexpensively. For ...
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3answers
117 views

Question on RSA trapdoor permutation

You plan to use a public-key cryptosystem based on the RSA trapdoor permutation in three different real-life applications, in which the attacker has, respectively, only one of the following resources: ...
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2answers
308 views

My SSH server public key is 2048 bits, but my account's private key is 4096. What is my effective security?

My SSH server has a 2048-bit public key. But my private key, for clients to login, is 4096-bit. In this case, do I have the brute force protection of 2048 or 4096 bits? My worry is that someone ...
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1answer
269 views

RSA smaller number work-out-by-hand not working - I think I made a mistake

I tried out the paper/pencil explanation @ http://sergematovic.tripod.com/rsa1.html, and it seemed to make sense just fine until I came to decryption. Here is what I worked out: Key Creation: Choose ...
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1answer
283 views

Why are RSA keys encoded with ASN.1 for TLS?

Browser vendors use ASN.1 encoding for RSA certificates in the TLS protocol. RSA public keys are just a number, so why do we need encode them to something else? That increases the risk of security ...
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2answers
101 views

In public key cryptography, how many keys are required for secure communication between n parties?

In public key cryptography, how many keys are required for secure communication between n parties? In my view the answer should be $n^2$. Reason: There are ‘$n$’ Parties. Every Party has One (1) ...
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1answer
51 views

Is the product of two primes only factorisable by those two primes? [closed]

The question is as per the subject line. Does the fundamental theorem of arithmetic imply (prove?) that if I multiply two primes, then those two primes are the only factors of the product? I.e. 17 x ...
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1answer
173 views

What does the cipher-text overhead means?

I have two questions here. What does the cipher-text overhead means? Why we were suggested not to encrypts the plain-text itself instead just encrypts only the key (i.e random number)
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1answer
117 views

Certificate == signed public key

For primes p and q used to create a keypair, I understand that the following operation is used to create a signature: $M^d (\bmod\ N)$ where d and N have their usual meanings and M is the message. ...
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1answer
52 views

What cryptographic paradigm is appropriate for this use case?

This is a very newbie question... I have to quickly implement a solution for our application that works like this... We have a binary executable that is given a configuration file. I need to encrypt ...
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1answer
119 views

Digital signatures under plain RSA

Show that digital signatures under plain RSA are insecure (Plain RSA means that signing is done by calculating $m^d\bmod n$, with $0\le m<n$, and no padding or hashing of $m$). Write an algorithm ...
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1answer
86 views

ElGamal encryption with private key [closed]

Does the encryption with a private key and decryption with a public key works in ElGamal likewise what is done when we use RSA for sender authentication?
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1answer
116 views

Is encrypting a public key with a symmetric key safe?

Assume the sender wants to share their ephemeral/long-term public key with intended receiver only and both share symmetric key. Is it secure to encrypt the (full/partial) public key (of RSA, ECC) ...
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1answer
153 views

I've got my private key compromised. How does CRL work?

How does certificate revocation list (CRL) work? How can I send a request to the CA to add my current private key to the CRL, so no one except me can add my certificate to the CRL? Related: - How can ...
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1answer
247 views

How does certificate-based encryption solve key revocation problem?

How does certificate-based encryption solve key revocation problem? For example, if a user accidentally reveals its secret key or an attacker compromises it, the user may request revocation of its ...
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1answer
84 views

How to choose the appropriate public (i, m) and private (j, m) keys?

I studied some encryption and decryption and I have found some very interesting problem to solve on the internet. I hope I am writing to right site - there are so many in StackExchange otherwise I ...
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1answer
148 views

Solving congruences using PARI

I'm having trouble finding info in the docs about how to solve a system of congruences. The closest I can find is 'matsolvemod' in here: ...
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1answer
141 views

Why is Blum-Goldwasser not IND-CCA-2 secure?

Consider the Blum-Goldwasser encryption scheme as described on Wikipedia. I was told that it was not IND-CCA-2 secure. I heard there was malleabilty, probably it has to do with XOR-ing. But I do not ...
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254 views

Can you help me understand ECC Cryptography and it's algorithm?

I want to know the basic understanding of ECC algorithm for cryptography. But I am not aware of the algorithm. Can anyone provide me with a basic explanation of the algorithm?
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2answers
108 views

RSA decrypting of a huge file by parts [closed]

I need to decrypt a huge file that I own previously encoded by myself with a RSA public key (it's possible for this step using a symmetric algorithm key). Problem is that I can't load it in my ...
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1answer
33 views

Is the private key static or variable key in the elgamal algorithm?

I read about elgamal algorithm it work like the follow steps Bashir chooses a large random prime p and a primitive root α modulo p. Bashir then chooses a random integer a with 2 ≤ a < p - 1 and ...
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1answer
52 views

Generating the keys for the RSA cryptosystem in probabilistic polynomial time

In general every public key cryptosystem ``has'' a probabilistic polynomial time algorithm $G$ such that $G(1^k)=(\textrm{public key}, \textrm{private key=trapdoor})$; $G$ is called the key generator. ...
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1answer
68 views

Key construction in the Full Cramer-Shoup cryptosystem

The Full Cramer-Shoup Encryption scheme needs to choose six random numbers from $\mathbb{Z}_q$, which we denote them by $ x_1,x_2,y_1,y_2,z_1,z_2 $. Then the scheme hides these random numbers in the ...
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1answer
165 views

how do you calculate the private exponent in asymmetric key encryption [duplicate]

Here is an excellent paper on the math of asymmetric key encryption: http://www.mathaware.org/mam/06/Kaliski.pdf‎ See the example on Page 6. The public key = $55$ Primes used to calculate public ...
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1answer
97 views

Generate random in secure message transfer

I’m doing a school assignment about secure communications between a Server and a Client. Basically, messages are exchanged between the clients and the server and these communications must implement ...
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1answer
770 views

GPG vs PGP vs OpenSSH and management of them

What is the main difference of the three? Can I use only one of them for everything (e.g. GPG for SSH authentication) If I encrypt my private key with a pass-phrase, is it strong enough so that if ...
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1answer
812 views

Why the following attack in common modulus RSA works?

Suppose that i share a common modulus $N$ with two users $u_1$ and $u_2$ with public, secret keys ($e_a,d_a$), ($e_b,d_b$). Why then $gcd(V,e_b)=1$ where $V=d_a*e_a-1/$W and $W=gcd(e_b,d_a*e_a-1)$ ...
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1answer
817 views

What is a trapdoor permutation?

Can anyone explain to me what a trapdoor one-way permutation is? Is RSA a trapdoor one-way permutation? Context: I was reading about ring signatures. On page 560, it describes steps to ...
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17 views

Questions about self-signed Certificates' Fingerprints and Client-Server Interaction through SSL [migrated]

I have some questions about how the fingerprint function is performed. First of all, I have some knowledge about cryptography. However it seems to do not be good enough to understand hundreds of ...
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27 views

Different between Shared Key and Common Key in DLP Application

What is the different between Shared Key and Common Key? Are they the same? Shared Key = Common Key?
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125 views

If H(m) = 0 for some m, how can a DSA signature be forged?

If we know for some message $m$ that $H(m) = 0$, how can we forge a DSA signature with only the public key? I got that $g^s*r = (g^x)^r$ where $x$ is the private key, but that's one equation with 2 ...
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217 views

Blum-Blum-Shub Cryptosystem

I am given $N$, which is Bob's encryption key. I was able to successfully factor $N$ into $N=p*q$. Alice encrypts a messages for bob and sends $a = [1,1,1,0,0,0,1,0,1,1,0,...]$ $b = 1545164156...$ ...
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71 views

hybrid PKE scheme CCA2 insecurity

I'm reading a paper here say: As we know, in hybrid PKE schemes XOR alone cannot perfectly hide challenge bit to the CCA2 adversary The author does not define hybrid PKE schemes. What is ...
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5answers
130 views

Symmetric encryption is no longer necessary?

Here is it: Symmetric encryption is no longer necessary, because all security services can be implemented with public-key cryptography. Moreover, in public key cryptography the operations for ...
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1answer
66 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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2answers
866 views

Where to store the private key and the public key in a communication protocol

I want to create a simple secured connection protocol over TCP/IP. I just want to connect from my mobile device to a server securely. Firstly I thought to use an SSL connection, but I changed my ...
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1answer
269 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
39 views

PGP message integrity : How can receiver of an email check the integrity using the sender's public key?

PGP message integrity: Basically, only private key can decrypt message encrypted with public key. But in the message integrity service in PGP does the reverse, where the Hash of the message if ...
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1answer
71 views

Is size Q equal to size SHA(Q)? [closed]

Assume d is a 128 bit random integer and P is base point of an elliptic curve and Q = dP is a point on the elliptic curve and SHA is a hash function with 128 bit output, my question is: Is size Q ...
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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
111 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
256 views

List of available symmetric & assymetric ciphers [closed]

I was looking all over the Internet list of ALL existing symmetric and asymmetric ciphers. I know that there's, for example, AES, DES, Blowfish, DSA. But how about more? Where to find such list?