Cryptography Stack Exchange
Cryptography Stack Exchange

Most Popular

more tags
1500 questions
11
votes
3 answers

Division in paillier cryptosystem

Is division possible in the Paillier Cryptosystem? i.e. given a the cipher-text $C$ of an integer $M$ the plain-text divisor $D$, and only the public key, can one compute the cipher-text of $M/D$ ?
user996522
  • 315
  • 2
  • 7
11
votes
2 answers

Consequences of AES without any one of its operations

Suppose AES-$128$. There are $4$ operations in AES's encryption, they are SubByte, Shift Row, MixColumns and AddRoundKey. Question: If I remove one of the following opearations, what will happen to the AES? SubByte, Shift Row, MixColumns If Shift…
Idonknow
  • 491
  • 8
  • 21
11
votes
2 answers

How secure is a pronounceable password in terms of entropy?

There are some strong studies which support the use of pronounceable passwords and multiple tools which provide generation of such passwords. According to this question the entropy of a password depends on its method of generation but how can I be…
Habib
  • 951
  • 8
  • 23
11
votes
2 answers

How large should a Diffie-Hellman p be?

In a Diffie-Hellman exchange, the parties need to agree on a prime p and a base g in order to continue. Assuming some application that's going to want to initiate handshakes with some large portion of its users, each of which only needs to be…
Inaimathi
  • 1,587
  • 3
  • 11
  • 15
11
votes
2 answers

How exactly does AES-NI work?

I am looking in to AES-NI which is now supported by many new CPU's and I have read a few papers which states that AES-CBC works faster with AES-NI, but I am unable to understand how exactly AES-NI works. As far as I know, AES-CBC encryption is…
rijndael
  • 471
  • 1
  • 5
  • 15
11
votes
1 answer

Efficient AES - Use of T-tables

I'm really in trouble! I'm trying to understand how the T-tables in AES encryption work. But I don't know if I get the point. What I understood is that they are used to reduce the whole computation of the iteration of AES just looking at the T-boxes…
gabribass89
  • 113
  • 1
  • 4
11
votes
1 answer

Regular MACs vs Carter-Wegman MAC

Carter-Wegman MAC variants (VMAC, UMAC etc) are known to be very fast and efficient when compared to MAC algorithms that are based on block ciphers and compression functions (like HMAC, CMAC etc). However, Carter-Wegman MAC variants are not very…
BlaX
  • 736
  • 7
  • 18
11
votes
1 answer

Homogenous vs heterogeneous unbalanced Feistel networks?

Unbalanced Feistel networks can be homogenous (F-function identical in each round), or they can be heterogeneous (F-function not always identical in each round). The advantage of heterogeneous UFNs is, that their internal properties change each…
e-sushi
  • 17,891
  • 12
  • 83
  • 229
11
votes
4 answers

How are timestamps verified?

You put an input and the hash value comes as an output then when someone puts the input the hash function it is applied to see if it is the same hash original value is stored in some database , that is how it works if I remember it…
100100001001
  • 111
  • 1
  • 1
  • 3
11
votes
3 answers

SHA256 output to 0-99 number range?

Is it mathematically possible to take a SHA256 hash and turn it into a 0-99 number where each number in 0-99 range is equally likely to be picked? As a 256 bit hash means the highest value possible is 2^256, this is not a nice or "round" number for…
John T
  • 477
  • 2
  • 4
  • 9
11
votes
3 answers

Associative standard cryptographic hash function

I am looking for a standard hash function which satisfies the following property: A hash function $H(a,b) = F(h(a),h(b))$ with $h$ (within $F$) any standard cryptographic hash function and $F$ an associative function. Is there any standard hash…
Mircea Ionica
  • 113
  • 5
11
votes
1 answer

curve25519 weak points for contributory behaviour

The Diffie-Hellman on curve25519 is usually calculated using the base point $(9,…)$ which induces a cyclic subgroup of $G:=\{\infty\}\cup(E(F_{p^2})\cap(F_p\times F_p))$ with index 8, i.e. there is a prime $p_1$ such that $|G|=8p_1$ and the order of…
Perseids
  • 562
  • 3
  • 13
11
votes
2 answers

Does the position of the salt improve its effectiveness when hashing?

Seems most documentation I have read suggests the salt should prefix the value to be hashed. Is this just for consistency, or is the salt more effective when prefixed?
Jim McKeeth
  • 931
  • 8
  • 16
11
votes
1 answer

ECDSA vs RSA: Performance on Android platform and surprising results

For our privacy-preserving protocol, an encrypted channel is established. In order to protect our system from man-in-the-middle attacks, a signature-based approach is used. After we've implemented it with RSA, we decided to optimize the protocol a…
OnTarget
  • 453
  • 4
  • 11
11
votes
1 answer

Tiger Tree Hash vs generic Merkle Tree

Is there any advantage of using Tiger Tree Hash over any other hash function organized as the Merkle tree? Are there maybe any properties of TIGER that, say, SHA-2 or BLAKE in Merkle tree do not have? And in general, is there any point of chosing…
toriningen
  • 473
  • 2
  • 12
1 2 3
…
99 100