0
votes
1answer
36 views

Prime Numbers in Discrete Log

Good day all, 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 ...
-1
votes
0answers
34 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
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
33 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}^{*}, ...
1
vote
1answer
31 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 ...
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 ...
-2
votes
1answer
48 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
-2
votes
1answer
45 views

What is Initialization vector (IV)

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?
0
votes
0answers
29 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 ...
0
votes
0answers
14 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
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?
0
votes
2answers
48 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 ...
1
vote
1answer
34 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
2answers
62 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
2answers
79 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 ...
3
votes
2answers
73 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) = ...
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
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 ...
0
votes
4answers
185 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 ...
-4
votes
0answers
47 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
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
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?
0
votes
2answers
67 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} ...
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: ...
0
votes
0answers
12 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 ...
-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
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 ...
1
vote
1answer
37 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 ...
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 ...
5
votes
2answers
71 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 $0 \oplus 1$? ...
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).
3
votes
1answer
42 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 ...
0
votes
0answers
27 views

Is AES-GCM length extension attack possible using authenticated decryption?

I am looking to encrypt a piece of data using AES-GCM with a full 16-byte GCM Tag and send it over the network using UDP. Is it safe to assume using the AEAD nature of AES-GCM that performing ...
-1
votes
0answers
30 views

Program implementation and flaws [on hold]

I had written an email encryption program in Java almost an year ago. I want to improve upon it and need your help in determining any obvious flaws in implementation and functionality. About program ...
-1
votes
1answer
44 views

why choose one-time signature ,not directly publish message [on hold]

why choose one-time signature for a message, not directly publish the message. Because we need to publish our public key on a reliable center (such as Trent), so why we directly publish message on a ...
2
votes
1answer
65 views

For which RSA moduli, precisely, is $e=d$ for all $e$?

This question shows that there are at least two valid RSA moduli $n$, namely $35$ and $91$, such that for any $e$ coprime to $\lambda(n)$, $$e^2\equiv1\mod\lambda(n)\text.$$ Reading the linked ...
0
votes
1answer
29 views

Specific example of a MAC in TLS?

This seems like quite a dumb question, but I really don't know if I'm finding a answer anywhere. I understand that if i access a website that is secured with TLS, we exchange ciphersuites and so on, ...
0
votes
1answer
55 views

Viability of an “Unconventional” Hashing Scheme?

I am playing around with the following hashing scheme: Start with a domain string (same for all users), Allow every user to mutate it in any way defining their own custom replacement rules, Append ...
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?
7
votes
0answers
93 views

How were shift amount constants in MD5 found?

The md5 specification gives a series of 4 rounds to execute over a 16-word block. Each round has a repeating sequence of 4 shift amounts (s in ...
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
1answer
52 views

Does a cryptosystem provide unconditional security if and only if it provides perfect secrecy?

Is unconditional security and perfect secrecy one and the same thing, i.e a cryptosystem provides unconditional security if and only if it provides perfect secrecy ? I've wondered about the above and ...
2
votes
1answer
53 views

Can a cryptosystem be unconditional secure if the same key $k \in \mathcal K$ is used for more than one encryption?

Can a cryptosystem be unconditional secure if the same key $k \in \mathcal K$ is used for more than one encryption ? I know that the one-time-pad doesn't have perfect secrecy and doesn't provide ...
1
vote
2answers
64 views

What makes an algorithm “fast in software” vs. “fast in hardware”?

When reading about different algorithms, I often encounter claims that various algorithms are "fast in software" (e.g. Salsa20) or "fast in hardware" (e.g. DES). What properties make a cipher ...
-1
votes
0answers
16 views

Client Emulation - Sending hexdump to server and getting response [closed]

So I used wireshark to retrieve a hexdump that has been encrypted with RSA. I need to figure out what the response to that would be when it comes back from the server. How I imagine it would work ...
0
votes
1answer
70 views

Find private exponent in RSA

The other answers for this confuse me, I know the principle of d in terms of the equation it has to satisfy. However I'm not sure how I would go about finding the private exponent without trial and ...
-2
votes
1answer
60 views

Best hash-algorithm [on hold]

What is the most secure hash-algorithm. Can you also give the second best and the third best like this: 1. Test 2. test 3. TEST I dont care about the performance
-3
votes
1answer
74 views

Alternative encryption algorithm

I need a alternative encryption alcorithm to AES. It shouldn't be AES, Twofish or Serpent and it must be very strong. I dont care about the performance.
0
votes
1answer
42 views

Post-quantum hybrid encryption

Assume the following simplified protocol: seed = curve25519SharedKey(theirPublicKey, myPrivateKey) sharedKey = scrypt(seed, salt, sufficientlyHardWorkFactors...) cipherText = aes256(sharedKey, ...

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