-1
votes
0answers
14 views

Terminology - hashing algorithm

From a definition stand point, can a hashing algorithm have more than one input, ex: hash(m1, m2, m3)? If not why algorithms like bcrypt, scrypt and pbkdf2 are referred to as password hashing ...
0
votes
2answers
28 views

Can Shannon's entropy be used to determine if a file is encrypted?

If we have to determine a file is encrypted or not, can we use Shannon's entropy algorithm on the file? As discussed here, the entropy (in bits per byte) being closer to 0 is considered as more ...
1
vote
1answer
18 views

How to meter and limit number of files encrypted?

First my apologies if this isn't the right forum for this but here's my problem : I have a black box that takes an input file and produces an output file. I want to sell this black box to a customer ...
0
votes
1answer
18 views

In which situation is HMAC mandatory rather than signature?

I’ve seen that the question has been asked already but this is still confusing to me. In a digital signature, Alice sends a message M and the ...
1
vote
1answer
9 views

HSM RNG - Compliance to FIPS 186-2

If the RNG of an HSM is said to be compliant to FIPS 140-2 (approved DRBG - SP 800-90 CTR mode) does also imply that it is compliant to FIPS 186-2 ? Thank you
0
votes
0answers
11 views

Homomorphic encryption implementation over circuits or assembly code [on hold]

I've looked at a few implementation of homomorphic encryption, such as HElib, but they only consider additions/multiplications and such. Is anyone aware of any implementation of homomorphic ...
0
votes
0answers
7 views

Entropy of Hash function [duplicate]

How is the entropy of the output of hash functions are defined? More specifically I saw in the paper https://eprint.iacr.org/2013/383.pdf Table 3 page 24. The entropy of challenge is mentioned which ...
2
votes
1answer
24 views

Proof for collision resistance on a block-based hash

I am designing an unkeyed hash based on the SIMON cipher. This is a follow up to “this” question. A quick summary: I have an ECC engine and the SIMON cipher in hardware, and it’s in an extremely ...
1
vote
1answer
24 views

Encoding an element in $r=r'||h(r')$ way

We consider a finite field $\mathbb{F}_p$, where $p$ is a large prime e.g. 256-bit. We have $b$ a fixed element of the field. We encode it as $b'=b||h(b)$, where $h(.)$ is a cryptographic hash ...
-1
votes
1answer
39 views

How to tell if an audio stream is encrypted or corrupted? [on hold]

Is the following stream encrypted or corrupted? I was on a call and then this happened: http://vocaroo.com/i/s0PlF2s8ULAU
-1
votes
0answers
31 views

How we compute distance after lshashing? [on hold]

If we use an lsh function under l2 distance (hw,b(x)= ⌊ (wTx)/r ⌋ where w is a d-dimensional vector with entries chosen independently from a 2-stable distribution, r is a positive real number) or ...
1
vote
0answers
21 views

Proof that two signatures are done with the same short bases

My question is regarding lattice based signatures. Each lattice can have multiple short (secret) bases. Is it possible to proof in zero knowledge that two signatures on a fixed lattice have been ...
1
vote
0answers
17 views

What is the exact algorithm and functions of the 4 way handshake?

I have to make a detailed diagram of the 4 way handshake and formulas for its functions so I need to know the exact process behind it. Like precisely what functions are used in it? I have been trying ...
4
votes
1answer
176 views

How should I read these three-dimensional (pseudo)random-generated numbers representations?

Visiting this site: http://lcamtuf.coredump.cx/oldtcp/tcpseq.html#phase I found graphical representations of random-generated sequence numbers, but I can't figure out how to interprete the plots. ...
0
votes
1answer
32 views

A5/2: Ciphertext Only Attack

A5/2 could be attacked with cipher-text only, using the Error Correction Code, in order to retrieve the session key. For the purpose of simplicity suppose that the error correction code copy the ...
12
votes
4answers
2k views

Which public key cryptosystems are not based on number theory?

Are there any public key cryptographic systems whose hardness assumptions don't involve number theoretic problems?
-2
votes
0answers
45 views

any post-shannon symmetric ciphers?

As far as I understand block ciphers use only simple operations to ensure good enough confusion and diffusion levels. meaning there is no math in it. "breaking a good cipher should require as much ...
3
votes
0answers
39 views

Does changing the order of the steps within a round affect the security of AES?

I was trying to understand the internal structure of AES (Advanced Encryption Standard) Standard order of steps within a round: Substitute Bytes Shift Rows Mix Columns Add Round Key Substitute ...
3
votes
1answer
44 views

What do the last chunks of the output string of Scrypt contain?

When you use scrypt to hash a string, it will generate something like: ...
0
votes
1answer
30 views

Why is symmetric lightweight crypto only about block ciphers and not about stream ciphers?

Why is symmetric lightweight cryptography only about block ciphers and not about stream ciphers? AFAIK stream cipher implementations cost at least three times less than block cipher ones?
1
vote
1answer
31 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
1answer
27 views

“NP-complete” authentication systems

Are there any symmetric authentication systems based on the hardness of an NP-complete problem? I understand that it doesn't really matter, since NP-completeness is about the worst case, and in crypto ...
1
vote
1answer
37 views

Rotating password with PBKDF2

Crypto is hard. Thank you for helping me learn. My encryption scheme currently looks like this: Salt is stored out in the open Secret is the user's password, known only to them EncKey||AuthKey = ...
-5
votes
1answer
38 views

pseudo-random-function

Please, can you help me about this question... Design a blockcipher E : {0, 1}k × {0, 1}128 → {0, 1}128 that is secure (up to a large number of queries) against non-adaptive adversaries, but is ...
-2
votes
0answers
28 views

Signing and hashing a new file detected in a folder [on hold]

I'd like to sign a file in a folder after detection. I'd also like to save a hash over the file to a text file. Thanks in advance!
6
votes
2answers
354 views

We can obtain “absolutely perfect CONFIDENTIALITY” using the one-time pad. Is there such a thing as “absolutely perfect INTEGRITY”? [duplicate]

The OTP (one-time pad) gives us perfect secrecy. This is the very best confidentiality available in this universe. (Although it does require large keys, which is beside the point of this question). ...
1
vote
0answers
40 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
21 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: <...
5
votes
1answer
120 views

How can I instantiate a generalized hash function?

I've come across a bunch of "strange" hash function notations, such as the following ones and now I don't know how to choose / instantiate them. Can you please explain me what this notation means and ...
3
votes
2answers
49 views

SHA-3 maximal number of zeros (Padding)

What is the maximum number of zeros, which are appended at the input- padding in messages? How large must the message be for this?
0
votes
0answers
24 views

elliptic curve and embedding degree

I am new in ECC. I am confused what the embedding degree in elliptic curve represents and what is the impact of its values on the curve and security ( small values or large values? What does the ...
2
votes
0answers
16 views

hash function notations and existing cryptographic hash algorithms [duplicate]

I am implementing Role-based access control by referencing the paper Enforcing Role-Based Access Control for Secure Data Storage in the Cloud. In page 6, they have mentioned to choose hash functions $...
1
vote
0answers
25 views

Hash function notations and their corresponding existing cryptographic hash algorithm

I am implementing Role-based access control by referencing the paper Enforcing Role-Based Access Control for Secure Data Storage in the Cloud. In page 6, they have mentioned to choose hash functions $...
1
vote
0answers
39 views

Build a hash function that returns a digest in $\mathbb{Z}_{N}^{\ast}$

I want to know if there is a way to build a Hash Function in a such way? $\mathcal{H}:{\left\{ {0,1} \right\}^*} \to \mathbb{Z}_{N}^{\ast}$, $N=pq$ and where $p,q$ are primes.
3
votes
1answer
47 views

How is a hash function that implements random oracle model collision resistance?

ROM is considered as collision resistance. Does ROM assume there is an infinite set of output, or assume the output set is always larger than the input set? Because by the pigeonhole principle, ROM is ...
2
votes
1answer
159 views

Prime factorization of 700 decimal digits number

I'm a newbie to encryption. If I create a number 'n' as a product of two prime numbers 'p' and 'q' with the following specifications: 'p' is a fully random prime with 300 decimal digits in length. 'q'...
0
votes
1answer
30 views

Getting the same two hash values for carved files I found

I am doing an independent study class for computer forensics, I have to carve the images I've been given. After using scalpel I get a .wav file and .asf file both files play the same songs, and they ...
0
votes
1answer
9 views

Fix timestamp of self signature on PGP public key [on hold]

I accidentally changed configuration of my pgp key while my system didn't have the correct clock. And I uploaded my key to key servers. Now every time I try to download my key from key servers or even ...
2
votes
0answers
20 views

What is bounded-retrieval model?

What is bounded-retrieval model in cryptography? How is it related (or apply) to leakage-resilient cryptography?
4
votes
2answers
467 views

Feistel-Network - why wire crossing?

In Feistel-Network, there would be a wire-crossing at the end (for the next round). Which insufficiency would occur, if the wire crossing would be omitted?
2
votes
1answer
27 views

Attacks from releasing decrypted CCM payload before verifying tag

CCM specifies (Section 1.7) that no plaintext data should be released before the MAC is verified. Why is this recommendation given and what attacks are possible against CCM if data is treated like a ...
3
votes
0answers
40 views

Attacking Scrypt Under Access Pattern Leakage

Could cache-timing channels (such as exist for certain block ciphers) somehow be made use of in order to extract memory-access pattern information if both the attacker and user are NOT in a shared ...
-2
votes
2answers
50 views

How to use modes of operation in DES? [on hold]

How to use modes of operation in block cipher with Data Encryption Standard (DES) ? How the Feistel structure properties are achieved in DES when a mode of operation such as ECB is used?
3
votes
0answers
39 views

Efficiency of oblivious algorithms vs non-oblivious algorithms

Recently, plenty of researchers are looking at designing efficient data-oblivious algorithms. Roughly speaking, an algorithm is said to be data-oblivious if its data access patterns are independednt ...
4
votes
0answers
37 views

Are any of the practical implementations of ORAM being used in a real world system?

The concept of Oblivious RAM (ORAM) was first introduced by Oded Goldreich and Rafail Ostrovsky in 1996. However, in the past 5-10 years there has been a surge in the amount of research that looks ...
-2
votes
1answer
38 views

How do I decipher a text using a repeating one-time pad?

I have an encrypted message that is 582 characters long. I know that: It is in hexadecimal It has been encrypted using a one time pad The pad's length is exactly 50 characters When the pad reaches ...
0
votes
1answer
31 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
23 views

Does changing an encryption key make an application unusable [on hold]

I have a small piece of basic PHP code that adds new users to a database. It was working fine yesterday but this morning I read something about encryption and realized I hadn't changed the encryption ...

15 30 50 per page