1
vote
0answers
10 views

CBC for Vigenere cipher

Suppose one uses the Vigenere cipher with cipher block chaining (CBC): Given the key $K$, the sequence $P_1, P_2, \dots$ of plaintext blocks is encrypted to $C_1 = P_1 + K \mod 26, C_2 = P_2 + C_1 + K ...
2
votes
0answers
17 views

How to convert AES to a PRNG in order to run NIST Statistical Test Suite?

I want to run statistical tests on my implementation of AES. How should I convert it into a PRNG? Is there a standard way to go about doing this? I could not find much information about this although ...
-1
votes
0answers
10 views

Use precomputed value (ECPoint,int) in Java BouncyCastle [migrated]

I am working with window-method multiplication in affine coordinates. Window Method ...
-1
votes
0answers
15 views

Would the rotors in Enigma machines always advance by one position? Or was there a way to set this?

Before encrypting a letter the first rotor advances by one, right? So there could be a way, once the first rotor turns 26 times, make the second rotor advance two positions instead of one. Or three. ...
0
votes
1answer
28 views

Can OTP be made practical by using stretched hash algorithms? [duplicate]

One of the main reasons for not using OTP in everydays life is that it is highly impractical - for encrypting 4GB of files we need a 4GB key that needs to be exchanged secure. I've had an idea on how ...
1
vote
1answer
38 views

“Royal Flags Wave Kings Above” [on hold]

I'm a starter to cryptanalysis and in fact to cryptology. Last night I was decrypting a message from a book that I would quite odd. It doesn't make sense. The decrypted message is "Royal Flags Waves ...
0
votes
0answers
25 views

construction of division polynomials

I'm not sure if this is the right place for my question.... I'm trying to understand the construction of the division polynomials used in the schoof algorithm. I firstly followed the report of ...
0
votes
0answers
14 views

Faster discrete Gaussian sampling

Our goal is find a faster discrete Gaussian sampling to solve $"SVP"$ problem in lattice: A lattice is discrete subgroup of $R^n$ such that define as below: let $\{b_1,\cdots ,b_n\}$ be a basis in ...
3
votes
1answer
17 views

Deriving a key for HMAC, using PBKDF2

What is the recommended way to derive a key for an HMAC-SHA256, from a passphrase and salt? I'd like to compute an HMAC-SHA256. I have a passphrase, and a message. I note that RFC-7518 (JWA) ...
5
votes
1answer
41 views

Performing simple arithmetic operations on compressed, and both compressed and encrypted data

We all know it is possible to perform addition and multiplication operations on encrypted data by means of homomorphic encryption methods. My questions are: Is there any cryptosystem that is able to ...
2
votes
2answers
40 views

How to generate a random number so server cannot cheat?

Here is the protocol: Bunch of players connected to server. Server creates nonce and hashes it - send hash to clients as bit commitment. Clients make nonces and send hashes to server as their bit ...
1
vote
2answers
29 views

NIST HMAC Test vectors

I am searching test vectors of the HMAC-SHA256 primitive to verify the correctness of an implementation. Without hesitation I go on the NIST website to see what they offer. While reading the ...
1
vote
1answer
15 views

Is this the correct procedure for cycle walking using an FPE?

To encrypt a value from a set (say a range of years from 1001 to 2001) Rank the set {0 = 1001, 1 = 1002, 2 = 1003...999 = 2001} Take the value you want to encrypt from the set (year = 1995) and ...
-2
votes
0answers
15 views

OCB(Offset Code Book) authentication encryption [on hold]

Can anyone give me ideas, how to implement Offset Code Book with authentication and encryption.
5
votes
1answer
111 views

Why was the Navajo code not broken by the Japanese in WWII?

In reading about this topic recently, to my understanding, the encryption schemes used on top of the Navajo language were very simple and definitely could have been broken (my research shows they ...
1
vote
1answer
33 views

Find the minimum Adversary's Advantage

I am wondering how to solve the problem below: Suppose we have a $MAC$ scheme $I=(S,V)$. There is another algorithm that can find a pair of texts $(m0,m1)$, with $m0≠m1$ such that $S(k,m0)=S(k,m1)$ ...
3
votes
2answers
114 views

What is the difference between SHA-3(Keccak) and previous generation SHA algorithms?

SHA-1 and SHA-2 share the same structure and mathematical operation as their predecessors - SHA-0 and MD5. Both SHA-0 and MD5 have been broken. This is one of the main reasons why SHA-1 is considered ...
1
vote
1answer
49 views

Secure randomized data matching?

This might be a dumb question but I will go for it. Let's say we have a data set $D$ consisting of sensitive data, and we want to be able to match if a new piece of data $S$ already exists in $D$ ...
2
votes
1answer
19 views

Merkle tree (dm-verity) with SHA-256 vs. SHA-1

Is there any knowledge or research on the use of different hash functions within a Merkle tree? My use case is file integrity protection. I am thinking about using different hash functions due to ...
1
vote
0answers
31 views

Data integrity using steganographic methods

I am looking for a lightweight and fast (almost real time) data integrity checker for a very time critical application. Is it possible to provide data integrity using a steganographic method, lets say ...
-1
votes
0answers
15 views

MitM attack in a comunication [duplicate]

Let's say A sends a message to B using RSA encription algorithm, the question is: How can C send a fake messagge to B pretending he's A? I thoutht that V should intercept all messaggess comming from A ...
4
votes
1answer
26 views

Can the backdoor in Dual_EC_DRBG be used to create a public key stream cipher?

Dual_EC_DRBG has the property that if $Q = e\cdot P$, someone who knows $e$ can break the PRNG. This seems to lead to a public-key stream cipher: Alice chooses a random $P, e$, where $P$ is a ...
0
votes
0answers
6 views

How can one securely hash passwords server side while avoiding DoS? [migrated]

It is generally recommended that one use a slow hash function to hash passwords. However, does this create a DoS risk?
3
votes
1answer
46 views

Multi-target attacks on AES-CTR with a random nonce

128-bit block ciphers are vulnerable to multi-target attacks where the attacker seeks to attack a collection of keys instead of a single key. A simple example: Generate keys $k_1, k_2, ...
1
vote
3answers
105 views

Security of a parallelizable block cipher mode

This is the scheme of a parallelizable block cipher mode of operation: $IV$ is the initialization vector. $BN$ is the zero-based index number of a block in a stream of data. $BT$ is the tweak that ...
-1
votes
0answers
39 views

Need help to find a tool that supports at least 1024 bit value to implement RSA algorithm [on hold]

I have implemented RSA on MATLAB but MATLAB dose not support 1024 bit value. It does not even support 128 bit value. It works well on smaller values but when the values of p & q are in millions it ...
0
votes
2answers
32 views

Is part of an output of secure PRNG also cryptographically secure?

Lets say I generate 192 bits using some secure PRNG. If I now take first 128 bits is it equivalent of generating 128 bits in the first place? P.S. More practical application for me is that I need a ...
0
votes
1answer
66 views

Secure blinding factor switching at malicious server-side (Switching in One Time pad)

Suppose all the values and operations are defined over a finite field $\mathbb{F}_p$ where $p$ is a large prime number. Assume all values are non-zero. Here $(z)^{-1}$ denotes multiplicative inverse ...
1
vote
3answers
90 views

Algorithms for Cyrillic encryption

I am working on a cryptography application which is to be used in my country. I tried looking up to see if there are any algorithms that support the Cyrillic alphabet, but I found none. Do you know of ...
1
vote
0answers
75 views

Block cipher not resistant to collisions

If we have the following block cipher, $E(k,m)$, which is a permutation, why is $f_2 (x,y)$ not collision resistant? $$f_2(x, y) = E(x, x \oplus y)$$
-4
votes
0answers
23 views

partition Recovery in windows 7

I encrypted a partition on my hard drive in windows 7 using bit-locker drive encryption, this partition was formatted, How may I recover it?
0
votes
0answers
14 views

Extension of Diffie Hellman for many participants [duplicate]

How to do the Extension of Diffie Hellman Algorithm for Multiple Participants
3
votes
2answers
49 views

Are there any practical methods of steganography?

There isn't a whole lot of information on steganography in the modern age, from what I can tell. A google search for steganography usually brings up a list of very impractical methods (e.g. tattooing ...
11
votes
1answer
762 views

How does a non-prime modulus for Diffie-Hellman allow for a backdoor?

Recently someone found that a Diffie-Hellman modulus used in a unix tool (socat) was not prime. This led some people to shout "backdoor". What I don't understand ...
0
votes
0answers
6 views

Generating Large Prime Numbers with Py Crypto [migrated]

I'm trying to generate a large prime number (2048 bits) using the crypto library in python in order to implement RSA. However, I do not really understand the syntax of the getPrime() function. I ...
1
vote
1answer
16 views

ABE Schemes - Access Structures & Performance

I'm reading this article, CP-ABE with constant-size keys for lightweight devices and in the Table 1, are there these access structure: Threshold, Tree, ($n$,$n$)-Threshold, LSSS, AND gates. I have 2 ...
3
votes
2answers
38 views

Determining Involutary Keys in Substitution Ciphers

How would I be able to show that a key $K=(a,b)$ is involutary for an Affine Cipher over the integers modulo n? Similarly, is there a way to generalize the conditions for a key to be involutary for a ...
1
vote
1answer
20 views

Key Exchange MAC encryption order of events? Problem

I want to write the sequence of events of how a MAC encryption works for documentation at work. For this purpose I have a document (given by my boss to me) in German and I am trying to translate it ...
1
vote
0answers
62 views

When we use one time pad TWICE in two different ways

Assumption and Notations: All the values defined over the field $\mathbb{F}_p$, where $p$ is a large prime number. We denote multiplicative inverse of value $v$ by $v^{-1}$. All values are non-zero ...
-2
votes
0answers
17 views

How to verify CURLE_PEER_FAILED_VERIFICATION, CURLE_SSL_CERTPROBLEM curl errors [on hold]

I want verify below two curl errors CURLE_PEER_FAILED_VERIFICATION, CURLE_SSL_CERTPROBLEM Please provide the source code or steps to verify above two error codes
1
vote
0answers
26 views

Need help with PKCS#12 3 key triple des key expansion

I am trying to decrypt PKCS8-Shrouded Key Bag inside a PKCS#12 pfx file. The oid for the encrypted data is PbeWithSHAAnd3-KeyTripleDES CBC. Iteration count and salt has been provided within the pfx ...
3
votes
1answer
69 views

How does RIPEMD160 pad the message?

For RIPEMD hashing algorithm on hardware I am not exactly getting how padding works So as per my understanding padding will work like explained below: For ripemd 160 message should be multiple of ...
0
votes
1answer
58 views

What is the complexity to break second preimage resistance?

In the context an of hash functions we have three required properties. Preimage resistance Second preimage resistance Collision resistance. The bounds for Pre image collision is $O(2^{n-1})$, the ...
0
votes
0answers
36 views

implementation of authenticated encryption algorithms on GPU

I am trying to implement an authenticated encryption algorithm on GPU. i have selected an algorithm that can be parallel both in Enc and Dec. this new authenticated encryption algorithm has a small ...
4
votes
2answers
90 views

Classification of a stream cipher

How would one classify a stream cipher that is neither synchronous, nor self synchronizing? I would have thought asynchronous, but from all the sources I can find, asynchronous is synonymous with ...
-4
votes
1answer
24 views

Computing inverses in a binary field

Please suggest how can i solve the below question What is the inverse of {03} in GF (2^8) with the irreducible polynomial x8+x4+x3+x+1?
0
votes
0answers
26 views

Effects of varying the key size for AES encryption [on hold]

How to investigate effects of varying the key size for aes algorithm encryption of data over the communication channel
0
votes
1answer
44 views

Elliptic curve ElGamal with homomorphic mapping

I am interested in ElGamal due to the fact that you can achieve some degree of homomorphic properties. I became interested in applying ElGamal to elliptic curves, and found this other question with an ...
8
votes
2answers
186 views

Would a Rubik's cube be a trapdoor function?

It's easy to scramble a Rubik's cube but it is hard to solve, unless you know the algorithms for solving it. This makes it a trapdoor function, correct?
0
votes
1answer
53 views

SHA1 collisions and the impact for ECDSA signatures

What will it mean for ECDSA using SHA1 when we have practical attacks breaking the collision resistance property of SHA1? [UPDATE] Added a bit more details to be clear. If $(r,s)$ is the ECDSA ...

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