Public key cryptography describes all cryptographic algorithms which have a pair of keys, one key that performs encryption and one key that performs decryption. One of these keys is made available publicly, allowing anyone to send messages that only the holder of the private key can read. You should ...
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public key distribution from a central server
I'm trying to code up a encrypted communication program. Originally I was thinking that I would use public key cryptography and then I would keep the public keys in a database where users could query ...
4
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70 views
How to build an electro-mechanical public key cipher machine?
It is generally assumed that asymmetric encryption schemes were invented in 1973 at GCHQ in Britain and, independently, in 1976 at the MIT. My question is, if the abstract idea of having a public key ...
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1answer
210 views
Can ElGamal encryption and ElGamal signatures be used together sharing the same key-pairs?
I'm working on a encryption system where each party can store exactly a single ElGamal private key in a device. This is a hardware limit. The system must be expanded to support signatures and ...
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2answers
2k views
In RSA, do I calculate d from e or e from d?
In the original paper introducing RSA, it is implied that one should first choose $d$ and then calulate $e$ from $p$, $q$, and $d$. However, I have found in other places (such as the wikipedia article ...
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1answer
47 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
74 views
What kind of cryptography should i use?
I have a trusted third part A that issues an access token (xml file) to an untrusted client C that uses this token to log into an untrusted server S and access to the authorized files.
I want only ...
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3answers
58 views
What are some good references for the implementation weaknesses in RSA
I'm pretty sure I understand textbook RSA.
Choose p and q, large primes, and compute n=pq.
Choose e such that $gcd(\phi(n),e)=1.$
Publish n and e.
Compute d such that $de=1$ (mod $\phi(n)$).
To ...
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1answer
81 views
Can you identify the public key used to encrypt something?
If I encrypt a string with a public key, does the encrypted ciphertext reveal the public key I used to encrypt it? Basically, I don't want anyone to know who the ciphertext is addressed to.
I'm ...
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3answers
18k views
Why is elliptic curve cryptography not widely used, compared to RSA?
I recently ran across elliptic curve crypto-systems:
An Introduction to the Theory of Elliptic Curves (Brown University)
Elliptic Curve Cryptography (Wikipedia)
Performance analysis of identity ...
2
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0answers
40 views
Key distribution and key exchange for simple secure FTP implementation [migrated]
I'm developing a simple secure file transfer protocol for a University project using openssl.
I have a Client (let be C) and a Server (let be S).
C will send to S messages like ...
2
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1answer
48 views
“proof of access” schemes
What is the state of the art way when implementing a scheme challenging a party to prove they have access to certain data?
What I'm looking for something along the lines of
Give them ...
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1answer
62 views
Is symmetric key encrypted with server's public key secure
I'm trying to implement lightweight yet secure protocol for communicating two trusted parties with each other.
Consider following scheme:
Alice wants to establish secure two-sided channel with ...
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1answer
56 views
Smart Card Basics
I want to implement some of the basic encryption algorithms on smart card, could any body guide me, how to program a smart card, which tools (hardware and software) i should have ,and are these tools ...
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1answer
40 views
When making public key fingerprints - is a sha1 hash still a good idea?
I'm thinking about trying to save some space (and readability) when referencing 2k and 4k public keys (millions of them) by storing the fingerprint in some places instead of the full public key.
...
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0answers
21 views
References on PKI [closed]
I hope this is the right forum. I don't see any PKI specific forum around here. Can somebody recommend some books/references on TLS/PKI? I am starting a project for secure document exchange among ...
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63 views
Certificateless Cryptography for Wireless Sensor Network [closed]
As we all know that ID-based cryptography has been implemented for wireless sensor networks, can we implement certifficateless cryptography over that? Discuss pros and cons.
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3answers
119 views
Requiring a “supervisor” key pair and a “user” key pair to decrypt multiple-recipient messages
I've been toying with some encryption scenarios recently. One of the hard ones I came across is a multi-party system.
So we have
Bob -- The person who sends the message (and knows it's recipients)
...
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0answers
75 views
RSA decryption from ciphertext using private key [closed]
I am sniffing a client side application traffic and I found some encrypted data. I am not able to decrypt it. Information which I have is
Public Key:
...
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0answers
64 views
how many bit flips current computers can carry per second? When brute force is hard?
How many bit flips the fastest current computers can accomplish per time unit? i.e per second. I am trying to find when brute force attacks are considered infeasible. The reason I chose bit flips is ...
2
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1answer
108 views
How does OAEP improve the security of RSA?
The heart of OAEP algorithm used for RSA encryption are the cryptographic hash functions $H$ and $G$.
Does everybody (so also an adversary) know these functions?
If YES: How does it help the ...
2
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1answer
119 views
Why does key generation take an input $1^k$, and how do I represent it in practice?
In my lecture, the lecturer said:
Let $K$ be the key generation algorithm. Given a security parameter represented in unary, $1^k$, $K(1^k)$ will output a keypair $(pk; sk)$, known as the public ...
3
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1answer
166 views
Secure encrypt-then-sign with RSA
I understand that when you want to encrypt and sign data with RSA the generally recommended approach is sign-then-encrypt.
However, I have encrypted data that I need to sign, to prove the author of ...
5
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1answer
116 views
Proof that padded RSA is CPA-secure
I'm referring to page 383 of J. Katz and Y. Lindell's Introduction to Modern Cryptography. The book presents a padded RSA:
${\bf Key Generation:}$ same as Textbook RSA (given security parameter ...
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2answers
89 views
standard way to authenticate parties with public keys without certificates
Is there some standard protocol for mutual authentication of two parties when there is possibility to use public key cryptography? The problem is that two parties can use public key cryptography but ...
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1answer
46 views
Adversary Two Stages
I am read this paragraph and I have a doubt.
"An adversary to PKC $\Pi$ is given by two probabilistic polynomial
time algorithms, $A = (A1; A2)$. In the first stage, the "find"
stage, the ...
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2answers
122 views
risk of attacker decrypting RSA ciphertext without public or private key
As I describe in my previous question I am trying to decide if it's worth it for me to use the Offline Private Key Protocol in creating some long term private archives, instead of just going with a ...
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1answer
83 views
How can a key pair be derived from an arbitrary hash?
If I correctly understand the concept of a "brain wallet" in BitCoin, you start with a passphrase, generate the hash of the passphrase, then somehow derive a public / private key from that to use as ...
3
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1answer
120 views
Combining AEAD with RSA
'Hybrid' encryption, where we combine symmetric encryption with public-key cryptography, is pretty 'tried and tested'.
To summarise, we generate a symmetric key and encrypt it using RSA. We would ...
10
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8answers
897 views
RSA with small exponents?
Just to establish notation with respect to the RSA protocol, let $n = pq$ be the product of two large primes and let $e$ and $d$ be the public and private exponents, respectively ($e$ is the inverse ...
1
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1answer
77 views
Which public key was used. PGP
Is it possible to find out which public key was used to generate the message?
Scenario is like this :
I got data which is encrypted with a public key. Now a "bad guy" hast the encrypted data, and ...
2
votes
1answer
58 views
What happen if a asymmetric crypto-system deals with only one key
Assume there is a crypto algorithm that deals with matrices to encrypt and decrypt. Regardless of the specification of such algorithm, what if the algorithm assumes that two parties can securely agree ...
2
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3answers
189 views
The utility of elliptic curve cryptography
Suppose that the only public key cryptography schemes that we knew were Diffie Hellman, RSA and ElGamal. How much would this set civilization back? Are there important applications of elliptic curve ...
2
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1answer
76 views
What's the probable usage of Interlock Protocol
I've recently read some articles about the Interlock Protocol, Article by Ron Rivest and Adi Shamir.
I'm wondering if it is possible to protect Key-exchange under Public-Key cryptography from the ...
2
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1answer
112 views
DLP based crypto systems with multiple independent generators
One example of a DLP based crypto system (or rather DDH based crypto system) where the public key parameters include two independent generators of the subgroup, is Cramer Shoup. Since the security ...
4
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2answers
183 views
Signature schemes for underpowered devices (8bit microcontroller)
I am currently researching into a small scale home automation system, aiming for cost. The system architecture is basically one master and several slaves which are connected in parallel.
Recently ...
2
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2answers
151 views
Assymetric password encryption - Viable? Which algorithm?
We have an application that requires cleartext passwords for user authentication because of the authentication mechanism in use (RADIUS/CHAP), which unfortunately we cannot change. Since we don't want ...
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1answer
56 views
EC equivalent for RSA-OAEP
I have some questions regarding aforementioned subject:
Is there a EC equivalent of RSA-OAEP key transport/encryption algorithm ?
Is ECIES-KEM sufficient ?
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1answer
104 views
Client and server using same SSL certificate - any issues?
I'm working on software where multiple components will communicate with each other using SSL.
There would be one central component acting as a server, which would also require the clients to present ...
7
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1answer
202 views
Alice trusts Bob only when Bob trusts Alice
some story first: Alice and Bob both have public/private key pairs. Now Bob wants Alice to sign his public key id. Alice agrees but only when Bob signs the public key id of her.
Is this something ...
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3answers
144 views
File encryption with one keypair?
I'm working on a program that uses an ECC keypair in a (password protected) PKCS12 file (.pfx) to encrypt files. I like this method because I think it will be higher security (using ECDH to negotiate ...
2
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0answers
21 views
Encryption with Deduplication [duplicate]
Suppose I have a file server running ZFS with file deduplication enabled, and I have two users that are sharing files: Alice and Carol. If Alice uploads huge_file.tgz to her www/ directory, and Carol ...
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2answers
171 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 ...
0
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1answer
63 views
Efficient algorithm for remainder calculation over prime field for ECC implementation?
I am working on 224-bit elliptic curve cryptography. In this 224-bit * 224-bit multiplication results 448-bit output. I am reducing 448-bit into prime field range( prime number $2^{224}-2^{96}+1$) ...
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1answer
50 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: ...
2
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1answer
219 views
Low Public Exponent Attack for RSA
I'm having trouble understanding the algorithm for finding the original message $m$, when there is a small public exponent. Here is the example I'm trying to follow (you can also read it in the 'Low ...
3
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1answer
281 views
Is a known plaintext, ciphertext, and public-key a viable attack on RSA?
Assume Alice and Bob are using RSA to create a common session key and Cindy is listening, attempting to obtain the session key.
Alice and Bob each have their public- and private-key pairs ...
0
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1answer
76 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 ...
4
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1answer
148 views
Question about why RSA is hard to attack
I think I understand why RSA is hard to attack but I'd like to get clarification if I actually do.
Assume there are two people, Alice and Bob, who are attempting to communicate privately but that we ...
2
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1answer
130 views
Generate an insecure public / private key pair
I am looking for a way to generate an "insecure" public key pair. and by insecure I actually mean a pair that is breakable using brute-force (or other encryption) methods.
As far as I know PGP ...
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1answer
111 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 ...
