0
votes
0answers
5 views

M3 Bitlocker Recovery

Has anyone used this software? Is this a legitiamate solution? I am working on rolling out bitlocker encryption on some devices and I want to have a data recovery plan in place. I am looking for ...
1
vote
0answers
12 views

What kind of obfuscation is used in this image? [on hold]

Edit: This is not off topic since I am not requesting analyzing or deciphering a block of data here. I'm NOT asking anyone to solve this, I'm looking for the name of the obfuscation technique used ...
3
votes
2answers
34 views

Is reusing keys for CBC and CBC-MAC secure when using encrypt-then-mac?

I know reusing keys is a bad idea, especially for CBC and CBC-MAC, but the example for why on Wikipedia seemed to use encrypt-and-mac. It seems obvious that the last block of encryption will be equal ...
1
vote
3answers
42 views

How is a message digest decrypted?

Trying to get my head around digital signatures and hit a slight block. The book I am using gives the following information Device A hashes a message to create a message digest Device A encrypts ...
1
vote
2answers
20 views

Linear cryptanalysis complete key guessing

In linear crypt analysis, partial sub keys are guessed and verified for its correctness with the help of plaintext and ciphertext. From the partial sub key, how it is possible to guess the complete ...
1
vote
1answer
12 views

OpenSSL & TLS1.2 with aes-cbc and initialization vector

I'm trying to manually decrypt DTLS traffic using OpenSSL and TLS 1.2. The cipher suite im using is AES256-SHA256 as listed here. Im able to decrypt the packets with the key that the server and the ...
1
vote
1answer
36 views

Ciphertext with uneven letter distribution

I have a ciphertext encrypted with an unknown method. It is part of a challenge (personal quest), so I can not post it. The letter statistics is the following: ...
0
votes
0answers
20 views

What are the pre-requisites I need to be able to code Salsa20 in C#?

I've taken a basic course in Cryptography and we've learnt various algorithms and their usage. I've implemented RC4 and Triple DES in C# with ASP.NET. For a project that I am a part of, I need to ...
100
votes
19answers
14k views

Time Capsule cryptography?

Does there exist any cryptographic algorithm which encrypts data in such a way that it can only be decrypted after a certain period of time? The only idea that I can think of, is something like this: ...
1
vote
0answers
18 views

How big window is secure and practical with TOTP? [migrated]

We are using Time-based One-time Password Algorithm (Google Authenticator) in our system. Since we currently don't allow any time window and code validity is just 30 seconds, we are constantly having ...
0
votes
1answer
29 views

RSA PKCS#1, v1.5 padding output

If I make use of RSA PKCS#1 in v1.5 what padding length is used. Basically, it is not allowed that the plaintext is bigger than the modulus. But what if the length in bits is the same (padding to ...
1
vote
0answers
12 views

Breaking Vigenere via Kasiski/Babbage method? (non-programmatic)

I'm really hoping someone can explain to me what is going on in the second major component of this form of analysis. If you wish, for convenience, here's a page that already has some ciphered text ...
1
vote
1answer
24 views

Why does a fixed key not make MACs like CBC-MAC or GMAC into secure hash functions?

Why does setting the secret key to a fixed, public value not make MACs like CBC-MAC or EMAC into secure unkeyed cryptographic hash functions? In other words, why is the resulting hash function not ...
0
votes
1answer
15 views

What is the time requirement for pairing computation and modular exponentiation?

I want to design a cryptographic protocol for encrypted search without pairing. I have seen some papers for protocols without pairing. How would I compare pairing computation and modular operations?
2
votes
2answers
44 views

Research for video game: Novice cryptography concepts

I'm making a video game which has some basic cryptography as a main base for puzzle design. I'm hoping players will get great puzzle challenge and learn a few cryptography concepts through playing the ...
-2
votes
0answers
11 views

Please help me decrypt this Classical Cipher [on hold]

Can any one help me decrypt this message: noohaiisee spyg iOyh h ol ceet pbcuoonnss
0
votes
0answers
6 views

How do you apply bilinear mapping to attribute based encryption?

I'm new to both bilinear mapping and ABE. I have a vague idea of how bilinear mapping works now, but I don't understand how it applies to ABE. Can someone give me an example?
5
votes
1answer
74 views

Encoding scalar values to points on Ed25519

I'm interested exploring key derivation and threshold signature protocol that require point arithmetic (addition) on the private scalar values and $S$ values of the signatures in ed25519. ...
2
votes
1answer
88 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? $$f_2(x, y) = E(x, x \oplus y)$$
10
votes
2answers
9k views

What is the difference between MAC and HMAC?

In reference to this question, what are the "stronger security properties" that HMAC provides over MAC. I got that MAC requires an IV whereas HMAC doesn't. I also understood that MAC may reveal ...
3
votes
3answers
23 views

What are possible caveats when generating a group for use as parameters for Diffie-Hellman key exchange?

As reusing a widely used group for Diffie-Hellman key exchanges might lead to far easier third-party key discovery through precomputation for that specific group, I would like to know what can ...
9
votes
3answers
1k views

McEliece Cryptosystem Implementations

Are there any current implementations (language irrelevant) of the McEliece Cryptosystem? I have been hunting around all day, and yet, have only found a few mathematical equations pertaining to the ...
5
votes
4answers
345 views

Get permutations from password

Are there any "good" ways to get a permutation from a password/pass-phrase? If one, for example, wanted to get a permutation of letters from a password, how might one do that in a smart way? I would ...
0
votes
0answers
13 views

Need CryptDeriveKey AES implementation in C#

I am integrating with 3rd party software that uses AES 128 encryption. I know this is not ideal, but the choice of encryption is up to the 3rd party software. I am using C#. My problem is in deriving ...
0
votes
0answers
22 views

Permuted Hash Table

Suppose we have a hash table, $HT$, consisting of $100$ bins.The hash table uses a hash function $H$ that is public. We all know that given value $a$ we can compute the address in the hash by ...
0
votes
2answers
24 views

OpenSSL Signature different each time

I have a file that I am generating a signature for using OpenSSL, and each time I generate the signature, it is different to the last time. ...
0
votes
0answers
24 views

Interesting Topics for Projects?

I hope this is not a off-topic question for the site, but I was wondering if I could get any recommendations for project topics in cryptography suitable for someone just learning basic material now. ...
1
vote
2answers
192 views

Simulation based proofs: Simple examples

I am aware that,(in theory) in order to proof that a scheme is secure using simulation based proof we replace an adversary in real world with a simulator in ideal world. Then we try to show that their ...
0
votes
0answers
22 views

How to create Crypto based Project

I took Cryptography course last semester and It was very interesting. To have a more practical understanding, I thought I should create a mini project. Below is the ...
0
votes
0answers
17 views

Poly1305 vs VMAC: is VMAC much better for long messages?

VMAC seems to me much more secure than Poly1305 on long messages (the security of the latter decreases linearly with increasing message length). Is this of practical relevance?
0
votes
1answer
37 views

AES128 Decryption in Objective-C just slightly off

I have been asked to integrate a home-grown CRM system with a 3rd-party data service provider (DSP). The DSP has encrypted the information they are providing. I only have their decryption ...
2
votes
1answer
78 views

How to find roots of equation $f(x)=0 \pmod p $, where $p$ is prime number?

$f(x)$is any nth degree equation $n>0$, how to find roots of $f(x)$ over prime modulo.
1
vote
1answer
46 views

Is multiplicative blinding less secure than additive?

It's easy to see that additive blinding (e.g., $x+r$ for secret x and random r) is perfectly secure in a finite field (this is a one-time-pad) and statistically secure for $r$ uniformly distributed in ...
-2
votes
0answers
19 views

block cipher secure as ind - cpa

if we have the following block cipher found here http://imagebin.ca/v/2WGa2kAGEX3E, is it ind - cpa secure?
1
vote
1answer
24 views

Updating values authenticated by Merkle Tree

Assume we have 4 values: $v_1,v_2,v_3$ and $v_4$. We construct a Merkle tree on top of them such that the values are leaves of the tree. I send the values and the tree to an untrusted server. But I ...
3
votes
1answer
62 views

What is wrong with simple concatenation in salted password hashes?

I once heard that if implementing a password hashing scheme, simply concatenating the password and salt together before hashing could lead to some subtle vulnerabilities, and I'm trying to figure out ...
0
votes
0answers
19 views

Miller Algorithm of Weil Pairing implementation for Python2

I would like to implement miller algorithm for Python, but it cannot work correctly, Please help me. (1) Please tell me Miller algorithm's output of the following case. ...
6
votes
2answers
771 views

Is there a null HMAC?

I came up with this question while unit testing a function that includes an HMAC. What is the expected behavior of an HMAC with a well-defined key and a set of data with no elements in it? Is there ...
4
votes
3answers
98 views

Common Modulus Attack not reproducible

I want to calculate a simple example of the RSA common modulus attack. However, the result is not correct and I do not find my mistake. p=$29, q=37, n=p*q = 1073, \phi(n) = 1008, e1 = 5, e2 = 11$ ...
1
vote
1answer
28 views

Cardholder to Merchant SET Protocol

I have some doubts regarding the SET protocol. Let say the Alice payment information runs through a sha-1 hash function which is a one-way algorithm, irreversible to create a message digest. How do ...
1
vote
1answer
35 views

Compression in key generation of DES algorithm

Does anyone have a pseudo-code or an algorithm or even a diagram of the compression (pc2) of the DES algorithm? I can't find a relation between the bits that are dropped, even when I do it manually ...
1
vote
2answers
57 views

How to encrypt incomplete block with RSA as a block cipher?

I have a question about an RSA academic example. If we are using block-RSA with a block-size of 3 and we have this message: "android". It is broken into 'and', 'roi', 'd'. How to encrypt the last ...
0
votes
0answers
23 views

SET Protocol (SET)

I would like to know if the current SET protocol uses 3DES or AES other than DES and RSA? I have look into many articles but some of them were outdated.
-1
votes
0answers
41 views

Encryption of Real Time UDP packet

I am planning to work on real time UDP packet encryption. I have a server which generates fixed size UDP packets at every 200ms and this message is sent to the receiver application which receives this ...
2
votes
2answers
120 views

Why does a non-prime DH modulus creates a “NOBUS” backdoor

can't we do a nobus backdoor with DH modulus prime? Some have argued that with a prime modulus you can just get the order by doing p-1 and then factor it, thus it is easy to reverse. I argue that this ...
1
vote
0answers
197 views

elgamal based decryption mixnet

Can anybody help me to understand elgamal based decryption mixnet? Pure elgamal can be used in mixnet (re-encryption mixnet) and its very easy, and I have implemented decryption mixnet using RSA also. ...
2
votes
0answers
50 views

How do substution-permutation networks work?

I understand what is going on in higher level. But I don't understand what's really going on in page 3 and 4 of this slide. Specifically, How $S_0$ and $S_1$ is used? What goes in what goes out? ...
-4
votes
4answers
90 views

How to break Universal Re-Encryption algorithm?

Let p be a prime, and g be an element of $ℤ^*p$ of prime order q. Let x ∈ ℤq be the private key, and $h = g^x$ (mod p) be the public key. To encrypt a message m ∈ $ℤ^*p$, pick two random ...
4
votes
0answers
65 views

How to prove that a function F isn't a pseudo random function

Let $F$ be a length-preserving pseudorandom function. For the following constructions of a keyed function $F' : \{0, 1\}^n \times \{0, 1\}^{n−1} \to \{0, 1\}^{2n}$, state whether $F'$ is a ...
3
votes
2answers
110 views

HW acceleration for Camellia cipher (x86_64/AES-NI/AVX2)

Modern processors support hardware acceleration for various crypto functions such as AES directly, or general vector operations which can be used in crypto ...

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