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.

learn more… | top users | synonyms (3)

0
votes
0answers
5 views

Creating a method to generate a pair of public and private keys and also ephemeral keys

I created a method to generate a pair of public and private keys and also emphemeral keys in java but it keeps returning errors. Listed below is my code but i am not getting the desired output. I also ...
9
votes
2answers
834 views

Public key cryptosystems not based on number theory

Are there any public key cryptosystems whose hardness assumptions don't involve number theoretic problems?
1
vote
1answer
26 views

In Paillier homomorphism how do you substract?

I'm trying to learn homomorphism so the problem may also be in my code (which I will include). I want to compute $a - b$ where $a$ is bigger then $b$. In order to do this I tried to compute $\frac{a}...
1
vote
0answers
37 views

Feasible attacks on ECRSA cryptosystem

In ECRSA cryptosystem, I want to know the feasible attacks. For illustrations we have two prime $p$ and $q$ such that $p \equiv 2 \pmod 3$, $q \equiv 2 \pmod 3$ and generate key pair as follows: $$n = ...
0
votes
1answer
20 views

In Paillier homomorphism, how do you deal with bit length? [on hold]

I'm trying to figure out homomorphic encryption and would like to multiply two paillier encrypted numbers. Like so: [a].[b]=[a+b] To try this I got this Paillier.java and tried the following: <...
0
votes
1answer
30 views

Do RSA keys contain a checksum mechanism? [duplicate]

I'm new to cryptography, and I was making an experiment a few minutes ago, but I want to have some deeper knowledge about RSA public and private keys. I have a set of keys One begins with ...
0
votes
0answers
53 views

Explanation of cryptographic terminology for newbies [on hold]

I feel like I'm making a mountain out of a molehill here, but I have (what should be) a relatively simple project, but the terminology used all over the Internet is either too simple or too difficult ...
-3
votes
0answers
75 views

Public-key Cryptography: I need a technical answer [closed]

So, I already understand the point of Public-key cryptography, and how it's supposed to work. I understand the basics, and I've seen way to many diagrams. What I haven't seen enough of, however, is ...
3
votes
1answer
84 views

Salting Hash stored on RFID tag?

In my application, I am trying to prevent counterfeit widgets from being used on our gadgets; think HP ink-cartridges. I will be doing such with UHF RFID tags embedded in the widgets. Unfortunately, ...
1
vote
0answers
31 views

Are public key and private key exchangeable? [duplicate]

If I get a key pair from RSA algorithm, can I make Private-Key public, and keep Public-Key secret without breaking the security of encryption and signature?
3
votes
1answer
58 views

Does encryption of data/information take place in peer to peer networks like Gnutella, Bittorrent?

Do peer to peer networks like Gnutella, Bittorrent have any encryption system to secure the users privacy or encrypt the file/data being shared? Elaborate please.
2
votes
1answer
64 views

Why is Diffie-Hellman used instead of just RSA in key-exchange (TLS, IKE)?

Why should a key exchange protocol (such as in TLS or IKE) use Diffie Hellman? Why not just use RSA? For example: Alice picks a random session key, signs it, encrypts it with Bob's public key, and ...
2
votes
1answer
88 views

Is this a proper key-exchange implementation?

I've been trying to implement Diffie Hellman key exchange so far from my own understandings (I know I could just stick with SSL/TLS, but I want to understand it in depth more), so I created this basic ...
1
vote
3answers
64 views

Is PGP's way of maintaining email security optimal? [duplicate]

I read a book called "computer networking: A top-down approach". It talked about how PGP creates an email message between Alice and Bob to maintain confidentiality, integrity, and authenticity. Let me ...
2
votes
0answers
25 views

Why SSH does not use a certificate authority in the same way as SSL [closed]

SSL requires the use of a trusted third party -- the certificate authority to verify a public key presented by a server to a client. SSH on the other hand relies on the client having the server's ...
3
votes
1answer
55 views

How to verify a sever's ECDSA fingerprint during SSH

I have read somewhere that Servers which have SSH access for users in the public can have their public key posted publicly (e.g., on a website), so that people who access such a server using SSH can ...
1
vote
0answers
24 views

To utilize asymmetric cryptography in symmetric manner - demand-of-security-definition?

Cryptography can largely be divided into two classes: asymmetric and symmetric. Like homomorphic encryption now greatly restricted in the asymmetric cryptography, the difference of asymmetric and ...
0
votes
1answer
69 views

What's is the simplest possible example of using cryptography to sign a message?

I am interested in explaining to a total layman the basics of how a network can know that you are authorized without having to compromise your private key. Using an example consisting of simple ...
3
votes
1answer
36 views

Is there a way to turn a PGP key into its semi-prime counterpart?

From my understanding of PGP keys they use the RSA algorithms to encrypt/decrypt messages. So, I know that the RSA algorithms use a semi-prime number to encrypt/decrypt messages. So, what I was ...
0
votes
1answer
58 views

Can you tell me how to create a cipher please? just a little simple one [closed]

I don't how to make a cipher text at all, can you help me?
4
votes
1answer
126 views

Why does choosing the first coprime e greater than half of φ(n) result in the same d (private exponent)

While reading on RSA's algorithm, I attempted a simplified implementation and noticed the following: When choosing the public exponent $e$, if the value chosen is the first coprime after $φ(n)/2$ ...
0
votes
2answers
71 views

Factoring an RSA modulus given high bits of a factor

I have {e,N,C} and part of p; can I get q from this example : ...
3
votes
1answer
36 views

How does this solution guarantee authentication of B and privacy?

The exercise is: What could be changed on the second message " Kya(Kxb(Ra,Ks)) " to guarantee B's authenthicity and also privacy? My teacher's solution was "add a destination" , so it would be ...
3
votes
1answer
52 views

Need help understanding this exercise's solution

We were given this exercise, which asks us to identify the types of keys used on this diagram: The solution was Kxa -> A's private key Kya -> A's public key KxB -> B's private key My question ...
0
votes
1answer
117 views

ECDSA non random k - Retrieve private key [closed]

At the moment I'm playing around with ECDSA. I know that I can retrieve the private key if the same K is used to sign two messages. I tried to use this script: Ruby Script to crack the private key. ...
5
votes
1answer
225 views

ECDSA key recovery - floating point values

I'm currently attempting to recover an ECDSA key. I have $m$, $m'$ and signatures $(r, s)$, $(r', s')$, and I know that $k$ is constant, the curve is NIST P-192 and the hash function of the. As such,...
1
vote
1answer
252 views

Is there a administrator key that can decrypt all ciphertexts encrypted with different keys by different persons in a group?

here is the scenario: $A, B, C, \ldots, Z$ are in a group with a administrator $Admin$, each of the users in the group has his own key $Key_A, Key_B$, and so on... everyone encrypt his own ...
0
votes
0answers
50 views

What are the most appropriate PKI based cryptographic protocols for peer to peer communicaton?

I've been trying to find out which is the most appropriate PKI based cryptographic protocol for peer to peer communication. I do understand that they vary with respect to the peer to peer architecture ...
1
vote
0answers
39 views

Key Distribution Center Key Protocol Analysis

As shown in the image, why is Circle 1 to be B and Circle 2 to be A? Why is not the opposite, that is, Circle 1 to be A and Circle 2 to be B? like this picture From my understanding, Notation B in ...
3
votes
1answer
39 views

Different kind of PGP keys or IDs, how to interpret them?

When people say "Here's my PGP key", they tend to come up with all sorts of different stuff. Sometimes they provide an 8-digit hexadecimal number, which seems to be a key ID (although I'm not sure). ...
0
votes
0answers
14 views

Why is a-symmetric so much harder to compute and why does it need such big keys? [duplicate]

I read that a symmetric encryption requires a way bigger key size to have the same security as symmetric encryption with smaller keys. But why is this, and why is it so much harder to compute?
3
votes
1answer
67 views

Can I change an encryption key used without decrypting first

I'm looking to solve for a little challenge I have in regards to changing the encryption on a message with asymmetric keys. I'd love to be able to swap the encryption to a different key in memory and ...
1
vote
1answer
27 views

Use MDC to provide origin authentication for public key encryption?

Why can't we use an MDC (“Manipulation Detection Code”, as also handled in this Q&A) to provide origin authentication when using public-key encryption?
1
vote
2answers
130 views

Where and how to store private keys in web applications for private messaging with web browsers

I am working on a web application enabling users to communicate over private messages which is just one part of the whole system. The main focus during my development process is to protect the privacy ...
4
votes
1answer
47 views

Padding schemes for asymmetric encryption with provable security in the standard model

Most padding schemes for asymmetric encryption (OAEP, OAEP+) are only proven secure in the random oracle model. Although no attacks are known, it would be nice to find a padding scheme with provable ...
1
vote
1answer
67 views

Creating ECDH using OpenSSL

For academic reasons, I'm playing around with OpennSSL 1.0.2g. I tested RSA encryption/decryption. I created key exchange with DHKE. But I'm struggling to find a way, to create ECDH, using only ...
3
votes
3answers
108 views

Can an adversary distinguish a private key from a pseudo-random string of the same length?

Apologies if this is a dumb question but allow me to describe the dilemma I have: Suppose that I am protecting a private key on a device using a password & PBKDF2. The obvious attack would be an ...
18
votes
4answers
4k views

Why does RSA need p and q to be prime numbers?

This is a clarifying thread after finding: What makes RSA secure by using prime numbers?. Despite the fact that this question was answered already, I am still struggling to really grasp the ...
4
votes
2answers
319 views

Security of the shared secret key for a smart meter (Linky)

Reading the specs of a new electricity smart meter (called Linky in France), I was surprised about the chosen encryption method (128 bits symmetric key AES), based on a single secret key (called CCC ...
1
vote
1answer
436 views

What is the random tape?

I am reading the paper "Toward plaintext-aware public-key encryption without random oracles" by Bellare and Palacio. So I can't understand what is the tape and random tape?
0
votes
0answers
59 views

How to calculate the exponent in modular exponentiation?

I have a problem when calculating power in modular, $a^b \bmod c = d$. where we can know values of $a$, $c$ and d, but we don't know values of $b$. example : $29^b \bmod 1024 = 365$. So, how can I ...
1
vote
1answer
30 views

How to add passphrase to an RSA key?

If I want to protect a private RSA key, do I just XOR the password into the key, or do I do something else? Is it secure? Edit: I got a good answer from a comment - Hash the password/passphrase with ...
0
votes
1answer
22 views

private-key can't be traced (GPG)?

I am very new to cryptography. I was reading about GPG/PGP Basics, and I have a doubt: As per my understanding, Everyone knows the algorithm (GPG) with which I generated my key pair. And If I give my ...
0
votes
0answers
30 views

Is a good idea to generate a public key from a secret key using a functional encryption scheme?

FE - functional encryption PK - public key I want to design a PK cryptosystem that has a unique PK for each encryptor. Namely, the encryptor submits a unique value (or an attribute) to the private ...
0
votes
1answer
45 views

How do you work out the private key in a RSA cryptosystem knowing a certain public key?

The public key: n = 85 and e = 19 I know that n is the product of two prime numbers, now is it right of me to figure them out by process of elimination which I got p or q equals 17 and 5. Or is ...
1
vote
0answers
97 views

Simulation-Based Proof: When a Secret Key is Involved

Assume we have a protocol in which a party receives an encrypted random polynomial. The polynomial is encrypted using his public key. We want to construct a simulator for this party (so this party ...
14
votes
2answers
1k views

NIST Diffie-Hellman prime: how was it picked? Where did it come from?

According to this Matasano Crypto challenge, the NIST "likes" the following prime modulus, which appears to be expressed in hexadecimal: ...