0
votes
2answers
102 views
Proper Way to Encrypt Data with Two Keys?
I'm going to develop a system that will have two keys. One supplied and generated by the system that's specific to an individual user and one from the user.
I plan on using AES.
Does it make sense ...
-1
votes
2answers
125 views
Computational indistinguishability and example of non polynomial algorithm
The wikipedia page on computational indistinguishability says that two ensembles are not distinguishable if "any non-uniform probabilistic polynomial time algorithm A" cannot tell them apart. To help ...
-1
votes
2answers
175 views
Cryptographic Symmetric Stream Cipher
Let me know a cryptographic symmetric stream cipher system with only two functions say S() and P() and it should satisfy the following conditions:
There will be two independent computers say M1 and ...
3
votes
1answer
503 views
Common Modulus Attack in a Lucas Group
I'm trying to decrypt a message that is encrypted using a LUC encryption scheme and running into roadblocks. I know that with RSA if Alice and Bob use the same public modulus but different encryption ...
2
votes
1answer
202 views
Are there any practical implementation of a homomorphic hashing or signature scheme?
A homomorphic hash function is a function $H : A \to B$ between two sets with some algebraic structure $(A, *)$ and $(B, \star)$ such that
$H$ is collision resistant, i.e. it is hard to find $x \neq ...
2
votes
1answer
233 views
Attacks on the RSA Cryptosystem
I was reading some articles about attacks on RSA system and I wonder about some generalization of the following theorem.
Theorem (Coppersmith).
Let $N=pq$ be an $n$-bit RSA modulus, where
...
1
vote
1answer
114 views
How to calculate y value from ((y*y) mod prime) efficiently
i am working ECC-224 bit. can any one tell me, how to calculate y value from ((y*y) mod prime) efficiently for large bit numbers.
0
votes
1answer
62 views
Which areas in CS will be (or have been) most affected by fully homomorphic cryptography?
I'm in the middle of planning a 5000ish word essay on fully homomorphic cryptography, the current practical implementations and their limitations.
Which areas of CS as a subject have been (or will ...
0
votes
1answer
71 views
Does SRP reduce to DH key echange when shared password is not secret?
I can find JavaScript implementations of SRP (Secure Remote Password protocol), but nothing that inspires confidence for Diffie-Hellmen key exchange. I also have a separate need for SRP later.
I ...
0
votes
1answer
59 views
How to make a message into a polynomial on NTRU encryption?
How to make a message into a polynomial on NTRU encryption? for example how we can conver 'hello world' to polynomial...
i have read the converting operation on IEEE Std 1363.1- 2008, but i can't ...
0
votes
1answer
126 views
Why is proof-by-reduction needed (for Elgamal proof of security, for example)?
The textbook proof for Elgamal encryption basically reduces to the Decisional Diffie-Hellman assumption (DDH).
Elgamal:
$Gen(.): x \xleftarrow{R} \mathbb{Z}_p$; $Enc(m,g^x): r \xleftarrow{R} ...
-1
votes
1answer
75 views
Which keys are necessary to decrypt Application data in a SSL connection?
I'm debugging an application which communicates between client and server using a SSL/TLS connection, and want to capture and analyze the sent data.
Are the client write keys and server write keys ...
-1
votes
1answer
41 views
Sematically Secure McEliece
I am read the Lemma 2 (pp13) in the paper [1]. Here a make a question Why "for any $Hash_z$ and any $Gen$"? The author of paper reply
The reason why "for any $Hash_z$ and any $Gen$" is that if ...
-1
votes
1answer
106 views
Chosen Plaintext Attacks
Assuming the ability to launch Chosen Plaintext Attacks (CPA), how many oracle calls an attacker
needs to break the affine cipher? and how
-1
votes
1answer
130 views
Fiat-Shamir signature
I have a question about Fiat-Shamir signature:
A hash function is h(w)=w mod 2011 and w1=2623, w2=3269, w3=1938.
What is h=? and how to determine k.t bits?
-2
votes
1answer
152 views
How does one find out ciphers/passwords without knowing what cryptographic algorithms are used?
If one does not reveal what cryptographic algorithms are used, how does a cracker find out a password/cipher that is used to communicate data? I heard that because there are methods to try cracking ...
0
votes
0answers
22 views
Kryptos : K3. What is the accepted transposition for a solution?
I'm studying the Kryptos sculpture with its cryptographic puzzles K1 to K4.
It's understood that K3 is solved via transposition, but I have seen several solutions. Which is the best/accepted one?
0
votes
0answers
39 views
Padding in PMAC
How does padding in PMAC work? I have been told two stories: Firstly, I have been told that it works similar to CMAC padding, and secondly, I have been told that it does not need padding.
I find the ...
0
votes
0answers
39 views
Security of .net AES implementation and security of a hash MAC
Hello I wanted to ask if there is any review about the security of the AES implementation of the .net Framework?
I found nothing concrete to that question, searching the Internet.
And, but this is a ...
0
votes
0answers
89 views
RSA and One Time Password (OTP) service
What is the expert cryptographic opinion on the following?
Assume that there is a web server and a client on web page.
User on the Client calls an OTP web service on the server which
a) creates a ...
0
votes
0answers
55 views
How compared encryption algorithm in terms of efficiency
I doing to compare two algorithm cryptography. first algorithm is RSA cryptography and second algorithm is El Gamal elliptic curve cryptography. now I want a way to compare between two algorithm by ...
0
votes
0answers
43 views
elgamal based decryption mixnet
Can anybody help me to understand elgamal based decryption mixnet? Pure elgamal can be used in mixnet (re-encryption mixnet) and its very easy, and I have implemented decryption mixnet using RSA also.
...
0
votes
0answers
178 views
Cryptographic Protocol using NaCL
Why?
I wanted to add some security and privacy to a chat-type server for playing various games (with a few things that are done on the server to limit cheating). Going by the "Don't implement ...
0
votes
0answers
78 views
Factorize RSA knowing several N and E
I did a CRT challenge yesterday and there`s one problem I was unable to solve, probably due to my lack of understanding advanced crypto math.
It`s about RSA. There are ten given pairs of N and E ...
0
votes
0answers
61 views
Is this a valid real-time authentication scheme?
The scenario in Alice/Bob/Cindy terms:
Alice approaches someone she doesn't know, but thinks is Bob, and asks for some secret information. Bob doesn't know and doesn't trust Alice, but Alice says she ...
0
votes
0answers
53 views
Timestamping services authorities, utilizing Linked, hybrid and other than PKI schemes
What are well respected Cryptographic Timestamping authorities utilizing more sophisticated than just PKI (RFC 3161) schemes, like Linked, Linked and signed, distributed hash trees (maybe P2P?), ...
0
votes
0answers
47 views
What happens when you use Windows credentials to sign a message?
I'm trying to dig into the messages that are exchanged when you sign a message using Windows credentials. I've modified the default service that is provided when you create a WCF service to use the ...
0
votes
0answers
74 views
Is this a secure multiparty protocol?
I am facing the following situation and i am trying to break down the problem into some specific cryptogrphic primitives.
There is a function F that takes as input a bit string and produces a ...
-1
votes
0answers
47 views
can we do double encryption of a message without first key?
Lets assume $k_1$, $k_2$ are two keys and there can be any relation between them like $k2 = E(k1) $ that is key $k_2$ is encryption of $k_1$ using some other long term key or any other relation.
...
-1
votes
0answers
37 views
Attacks on a stream cipher
What attacks are there against stream ciphers?
I found 2:
Bit-flipping attack. Since every input bit mention exactly one output bit, it is possible to change ciphertext bits where the corresponding ...
-2
votes
0answers
53 views
Is the likelihood of a birthday collision linear (evenly distributed) for all ciphers? When are they not?
When discussing the Birthday Principal, in combination with the pigeon hole principal, it was argued that an uneven distribution of birthdays (bias for September and any Tuesday of the year) made ...
-2
votes
0answers
66 views
One time Pad Adversary
I like know Why $Pr[\mathsf{PRIV_{EAV}}(\Pi,A,n)=1] = 1/2$, when $\Pi$ is a One Time Pad. I trying:
$$Pr[\mathsf{PRIV_{EAV}}(\Pi,A,n)=1] = Pr[b'=0|b=0]Pr[b=0] + ...
