0
votes
1answer
13 views

Can I simulate AES-ECB with other block cipher mode?

I am trying to write some code using the Web Crypto API (http://www.w3.org/TR/WebCryptoAPI/#algorithm-overview) which provides only some of the block cipher modes for AES, intentionally excluding ...
0
votes
1answer
14 views

what is wrong in my Rijndael that gives me this?

I'm using the Rijndael classes from .net System.Security to Encrypt my RSA Keys this is how I set it up: ...
0
votes
1answer
43 views

Prime Numbers in Discrete Log

I am implementing a security protocol based on discrete log. I came across the equation $p = kq + 1$. Understand that based on number theories that both $p$ and $q$ should be large enough to be ...
0
votes
0answers
17 views

Diffusion in Stream Cipher

The diffusion property of a cipher defined by Shannon refers to the ability of a cipher to cause a lot off bits in the cipher text to be modified when even a single bit in the plaintext is flips. ...
0
votes
1answer
19 views

Encryption and HMAC in a PSKC file

This is the PSKC standard https://tools.ietf.org/rfc/rfc6030.txt In Section 6.1 6.1. Encryption Based on Pre-Shared Keys They have the following ...
1
vote
0answers
25 views

Show that $-3P_1-2P_2+6P_3=0$

If $E/\mathbb{Q}$ the elliptic curve $y^2=x^3+x^2-25x+29$ and $$P_1=\left (\frac{61}{4}, \frac{-469}{8}\right ), P_2=\left ( \frac{-335}{81}, \frac{-6868}{729}\right ) , P_3=\left ( 21, 96\right )$$ ...
2
votes
1answer
41 views

Why should an Initialization Vector (IV) be supplied externally

My software uses a 3rd party encryption appliance. One of the capabilities they allow is for client software to supply an IV. i have been trying to understand - why would they not generate a random ...
8
votes
4answers
1k views

Why shouldn't I use ECB encryption?

I'm using Java to generate encrypted strings, and I get this warning at build time: ECB encryption mode should not be used So I'm wondering why I shouldn't use ECB and what I can use instead?
1
vote
1answer
88 views

Protocol composition [closed]

I have been trying to wrap my head around different definitions of protocol security (stand alone, sequential composition, parallel composition, universal composition) and how the proofs of any of ...
1
vote
0answers
697 views

Ransomware RSA-1024 encrypted files [closed]

Sorry if this is not the right place to ask this question, but it seemed most relevant to the Cryptography topic. One of the users on our domain was infected with a ransomware virus that caused all ...
1
vote
1answer
152 views

Generalize the Merkle–Damgård construction for any compression function

I am trying to figure out this question: Generalize the Merkle–Damgård construction for any compression func­tion that compresses by at least one bit . You should refer to a general input ...
0
votes
0answers
42 views

How to verify the result of repeated squaring method

I am wondering that is there any way to check that the result of repeated squaring is correct or not Suppose we have a calculator (like Casio FX 570ES, ...), and we want to calculate x^d ≡ n If any ...
0
votes
1answer
37 views

Luby-Rackoff on Feistel ciphers

i looked here: http://www.icg.isy.liu.se/courses/tsit03/forelasningar/cryptolecture04.pdf on page 46. It seems to say that if we have a Feistel cipher, and plaintexts $(L_0, R_0)$ and $(L_{0}^{*}, ...
0
votes
0answers
17 views

AFV11 scheme simplification

I tried to implement AFV11 scheme http://eprint.iacr.org/2011/410 and faced with performance issues. In order to reduce this issue I have made some simplifications to the scheme. Does the following ...
-1
votes
0answers
35 views

Is my itsdangerous replacement secure?

I'm working on a library related to this question on StackOverflow. The purpose of the library is to address some of the limitations in itsdangerous, enumerated here. "I think I have done a good job", ...
0
votes
0answers
31 views

Example related to Algorithm to invert VMPC function

I am new with VMPC one way function. I understood the concept from vmpcfunction.com. But I can not understand algorithm of inverting VMPC function.I am not getting any example of it with detailed ...
1
vote
2answers
84 views

how to let other people respond to emails only decrypt-able with my private key

First of all I have to say it's a homework question but since I have no one to consult with, I ended up here :) Suppose a case in which you are the manager of a company and all employees encrypt ...
0
votes
1answer
46 views

Calculate number of chips to solve bit commitment using hash function

I have a problem that I don't know how to solve Assume that H is a cryptographic hash function with output size 80 bits. Assume that ABC123 is a specifically designed line of hardware chips for ...
-2
votes
1answer
53 views

Which Block cipher mode should I use? [on hold]

Which of the Block cipher mode is MOST secure? I dont care about the performance just the most secure
0
votes
2answers
51 views

Embedded devices Authentication, Integrity and Confidentiality

Embedded devices send messages to the server. The server occasionally sends messages to individual devices(Reboot, upgrade firmware etc) After some research this is my ad-hoc solution: 1) Each ...
-2
votes
1answer
48 views

What is Initialization vector (IV) [on hold]

I am not the best cryptologer and therefore I have some questions so I learn more and get better. Heres the questions: What is Initialization vector (IV)? MUST I use it or not?
1
vote
1answer
38 views

Associative but NOT Commutative Reducing Function Construction with Existing Hash Function(s)

Is it possible to construct a binary reducing function based on any existing cryptographic hash function satisfying the associative property but not the commutative property? So formally: Using an ...
1
vote
2answers
44 views

Chosen plaintext vs Chosen ciphertext

What is the difference between chosen plaintext and chosen ciphertext attack? In both of these adversary has access to paintext-ciphertext pairs.Then where lies the difference?
-4
votes
0answers
48 views

Is this cyphering method a really durable breakthrough innovation ? or not [on hold]

I know, Security Breakthrough Innovation is quite "a {m,b,t...}illion throws for one hit" Furthermore, I am not a Cryptopath. Nor a Professional Paranoid. The keys: - why byte? byte is the ...
2
votes
3answers
89 views

Computation indistinguishability questions

The definition I have is: Two probability ensembles $X = \{X_n\}_{n \in \mathbf{N}}$ and $X = \{Y_n\}_{n \in \mathbf{N}}$ are computationally indistinguishable if for every probabilistic ...
16
votes
5answers
446 views

Why are primes important for encryption

Why are primes so important? Why can't we just use a random number? My guess is that it's because finding a random prime require more computing power, than finding a random number. Can anybody confirm ...
2
votes
2answers
63 views

Security concern about reducing hash value using modulo operation

As stated in the title, what I am looking for is information about a "technique" that I would like to use in some of my algorithms. Sometimes I need to map a hash function's result into a range of ...
1
vote
1answer
35 views

test vectors for 3DES seem to in fact be testing DES - not 3DES

NIST SP 800-20 Appendix A has what presumably are supposed to be test vectors for 3DES except almost all of the test vectors utilize 8-byte keys and not the 24-byte keys that 3DES is supposed to have. ...
-4
votes
0answers
28 views

Research Topic - lattice theory and cryptography [on hold]

Am planning to do research and in the process of selecting a topic . Request you to tell if concept of Lattice theory- Boolean Algebra can be used in Cryptography. If yes please suggest areas which ...
2
votes
1answer
83 views

Gap problem for Learning With Errors

Informally, a "Gap" problem is the one that arises when solving the computational (or search) version using an oracle for the decisional version. For example, the Gap Diffie-Hellman Problem (GDH) is ...
0
votes
1answer
46 views

Modular Reduction of polynomials in GF(2^m)

Hello I am having trouble understanding the algorithm implementation in hardware of the reduction process over galois fields of F(2^163) In the following process it ...
3
votes
2answers
74 views

Second pre-image resistance vs Collision resistance

From Wikipedia: Second pre-image resistance Given an input $m_1$ it should be difficult to find another input $m_2$ such that $m_1$ ≠ $m_2$ and $\operatorname{hash}(m_1) = ...
0
votes
2answers
325 views

Why can't Homomorphic encryption schemes support algorithms with conditions/branching?

If it isn't already apparent from the title of my question, i should make clear that I have only a very basic understanding of homomorphic encryption. I would like to know why homomorphic encryption ...
3
votes
2answers
123 views

Which multiplicatively homomorphic encryption scheme supports encryption of 0?

I want a multiplicatively homomorphic encryption scheme that supports encryption of 0 (e.g. Elgamal doesn't support). I also want the multiplication to be operated on the ciphertext of 0, i.e., if ...
1
vote
1answer
30 views

KPA on Feistel cipher?

I heard that DES is technically “broken” because of attacks involving large amounts of known plaintext. These attacks are obviously academic and highly complicated, so for some intuition I was hoping ...
1
vote
2answers
75 views

Significance of 3mod4 in squares and square roots mod n?

Why do most literature while discussing squares or square root modulo a prime P, consider P to be congruent to 3 mod 4?
0
votes
4answers
186 views

Do Brute-Force Attacks and Cryptanalysis refute Kerckhoffs's principle?

According to Kerckhoffs's principle "A cryptosystem should be secure even if everything about the system, except the key, is public knowledge." Now I want to throw in a provoking formula of mine which ...
5
votes
2answers
72 views

power consumption in a XOR

I'm trying to understand how a XOR affect traces of power consumption in a Differential Power Analysis on smartcards. What's the difference in energy radiated in a $1 \oplus 1$ and in a $0 \oplus 1$? ...
0
votes
2answers
68 views

Brute force against computational security

One-time pad is secure under brute force with respect to either of the definitions \begin{align} \Pr[M = m] &= \Pr[M = m | C = c]\\ \Pr[C = c | M = m_0] &= \Pr[C = c | M = m_1] \end{align} ...
-2
votes
0answers
21 views

Simple Encrypted Message, With Key Included [on hold]

Hi minds of Stack Exchange, today I present you the mysterious message that has been troubling my mind for the past one hour: From: 25 - 5()1 - 31 - 15(-)d Grade: 55 - 2(-) Class: 44 - ...
3
votes
1answer
56 views

Proving the existence of a pseudorandom function

I've been reading the Introduction to Modern Cryptography book by Katz and Lindell as part of my own learning and have come across this exercise which I am not sure how to approach. The exercise is: ...
3
votes
2answers
36 views

How many times can a key be used for HMAC-SHA256 before it needs to be rotated?

If I wanted to use hmac for proving that a value hadn't been tampered with, how many times can I use a key before it needs to be rotated?
4
votes
1answer
129 views

Compact digital signature for noisy data

The question asks for a signature scheme, with a public verification procedure, that is tolerant to minor alterations of the signed data during its transmission [possibly in analog form over some ...
2
votes
1answer
142 views

Using modulus in one time pad?

I would like to know what is the real purpose of using a modulus in the equivalent of a Vernam cipher: Data $d$, large number $M$. Assume the key length is $\lambda$ bits. Then $M$ could be ...
-1
votes
1answer
20 views

Synchronize one time password algorithm [on hold]

I have an iOS application and php server . I have searched a round TOTP and found some open source about objective c and php . but when comparing between token from php and iOS application its ...
0
votes
0answers
13 views

Modifying algebraic secrecy message to use digital certificates

I have the following message: sign((M’, T$_A$, sign((encrypt((encrypt(M, $K_{pbB}$), M’), K), T$_B$), $K_{sB}$)), $K_{sA}$) Sign is used for signature generation. Encrypt is used for ...
6
votes
2answers
467 views

Implement deniable encryption with AES/RSA

I'm on a crypto app using OpenSSL (I'm more an implementer/cryptographer than a cryptologist), mainly as a hobby, for now. My app will be able to encrypt a file (not a container) with symmetric or ...
0
votes
0answers
38 views

Obliviously computing the Least common multiple of two poylnomials

Consider I have two polynomials $f_1$ and $f_2$ of the same degree. I want to secure them (using any kind of encryption except FHE) and outsource them to an untrusted server. I want him to compute the ...
3
votes
1answer
43 views

PBKDF vs HKDF for pretty long key

I'm developing a messenger application with encrypted chats. In the first version of the app I've used PBKDF2 (10000 iterations, SHA1, random salt) to extend a short user password and generate keys ...
2
votes
1answer
60 views

Encrypting decryption key

What's that property called when a scheme is secure even if you encrypt the decryption key? Some schemes have problems when your plaintext is the decryption key (or just the key if symmetric).

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