5
votes
3answers
186 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?
3
votes
2answers
61 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 ...
2
votes
0answers
91 views

Which gives better deterministic encryption SIV or Plain ECB mode?

Lets say , if we encrypt a plain text message $msg$ with key $key$ in below two ways. Which is the below would give better deterministic encryption and why ? AES-ECB($key$ , $msg$) SIV($key$, NIL , ...
0
votes
0answers
6 views

Modifying message to use digital certificates

I have the following message: sign((M’, T$_A$, sign((encrypt((encrypt(M, $K_{pbB}$), M’), K), T$_B$), $K_{sB}$)), $K_{sA}$) How would i modify this message where a digital certificate is used by ...
1
vote
1answer
72 views

Polynomial division hardware implementation

I am beginning the implementation of the polynomial binary division algorithm now as I understood i will be checking the MSB bit if 1 to XOR and shift the sum if 0 i will only shift. What I am not ...
0
votes
0answers
18 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 ...
0
votes
0answers
4 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, ...
-2
votes
1answer
47 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
0
votes
1answer
52 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 ...
5
votes
0answers
27 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 ...
5
votes
1answer
816 views

On-the-fly computation of AES Round Keys for decryption?

The usual implementation of AES first computes all the Round Keys sequentially starting from the key, and stores them in RAM for later uses. However, when enciphering a single block with a key that ...
7
votes
3answers
435 views

How Brittle Are LCG-Cracking Techniques?

There are published techniques for cracking LCGs, but to my eye those techniques seem very brittle — very minor changes can add nonlinearity that renders techniques like the LLL algorithm unusable. ...
-3
votes
1answer
52 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
0answers
29 views

Probability of a bit changing SHA-1

I'm looking at diffusion (avalanche) in SHA-1, and how strong it is. I've seen on wikipedia that 'When a single bit is changed the hash sum becomes totally different.' ...
1
vote
1answer
44 views

Protecting a short password

I figured that a really secure password would be an AES 128 key. If this key were to be base 64 encoded, I could replace 4 random bytes in it in order to make it unusable unless you know which bytes ...
0
votes
0answers
7 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
30 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 ...
2
votes
1answer
49 views

OpenSSL des-ede3 not producing same output as test vector implies it should be

I'm encrypting one of the standard TDEA/3DES/DES-EDE test vectors with openssl: ...
1
vote
2answers
38 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
vote
1answer
24 views

Does a cryptosystem provides 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 ...
-1
votes
0answers
13 views

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

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
134 views

AES Affine Transformation in $GF(2^4)$

in $GF(2^8)$ the AES affine transformation is defined as \begin{equation*} b( x ) = ( x^7 + x^6 + x^2 + x ) + a ( x )( x^7 + x^6 + x^5 + x^4 + 1) mod (x^8 + 1) \end{equation*} where the polynom $( x^7 ...
1
vote
2answers
121 views

How can a cryptosystem be unconditional secure?

How can a cryptosystem be unconditional secure ? The definition of an unconditional secure cryptosystem states that the cryptosystem cannot be broken even with infinitely computational ressources ...
0
votes
1answer
35 views

Post-quantum hybrid encryption

Assume the following simplified protocol: seed = curve25519SharedKey(theirPublicKey, myPrivateKey) sharedKey = scrypt(seed, salt, sufficientlyHardWorkFactors...) cipherText = aes256(sharedKey, ...
3
votes
1answer
54 views

Formal relationship between encryption and random number generators?

Cryptographically secure random number generators seem to have similar properties to symmetric encryption: initial seed is permuted to produce a random numbers (key and ciphertext) given the seed, ...
2
votes
1answer
43 views

How to implement homomorphic multiplication for Elgamal?

I want to add the homomorphic property to Elgamal in libgcrypt. This is the core code I added to the library. ...
2
votes
1answer
42 views

Committing Bilinear equation in Groth-Sahai framework

Groth-Sahai framework enables us to commit to QE, MSME, PP equations. Now, is the equation below committable in GS framework? A bilinear map $e: G_1 \times G_2 \rightarrow G_T$. $g_1 \in G_1$ and ...
-2
votes
0answers
21 views

Generating a code from package name of android apps [on hold]

Consider an application which generates a long code from package name of applications. For example: ...
2
votes
1answer
92 views

How to use ElGamal to encrypt zero?

ElGamal encryption algorithm is as follows: To encrypt a value $m$, it chooses a random value $r$, and calculates $c_1=g^r$ $mod$ $q$ $c_2=m*h^r$ $mod$ $q$ where $g$ is the group generator, $x$ is ...
2
votes
1answer
102 views

Calculate the security of a cascade cipher

I’m reading “The Security of Multiple Encryption in the Ideal Cipher Model” and I’m having a hard time understanding something. How do I calculate the bounds of cascade cipher from the following ...
2
votes
1answer
97 views

To prove $r \cdot f_1 +f_2 \cdot (s+1)$ is secure

We define the polynomials $r, f_1,f_2,s \in R[x]$. Where $r$ is a random degree 1 polynomial and $s$ is a random polynomial such that: $degree(s)=degree(f_1)=degree(f_2)$, let $R$ be $\mathbb{Z}_p$ ...
1
vote
1answer
83 views

Are there signatures that don't have subliminal channels?

Are there signatures that don't have subliminal channels and also don't require commitments or zero-knowledge proofs? DSA or Shorr signatures need a nonce which can leak valuable information. There ...
1
vote
0answers
166 views

Ransomware RSA-1024 encrypted files [on hold]

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
0answers
40 views

Signature verification with only hash (without full data)

I am looking for a way to sign a file, such that someone else can verify that I had this file, even if they only know a hash. I want to prove that I have the full file to someone who only has the ...
1
vote
1answer
26 views

what are the plaintext's for the RC4 stream cipher test vectors in RFC6229?

https://tools.ietf.org/html/rfc6229 has stuff like this: ...
-1
votes
0answers
49 views

how can I understand nonlinear coding for error detection

I want to understand how nonlinear coding can detect the errors in cryptography computing . actually I don't know what these code doing and what are the codewords in this system. now can any body ...
1
vote
0answers
35 views

What is the fixed point attribute of DES (when used with weak-keys)

I've heard in some lecture that the weak keys in DES implies the existence of $2^{32}$ fixed points in the algorithm, i.e. that $DES_k(x)=x$ for $2^{32}$ such $x$'s. I couldn't find anything about ...
1
vote
0answers
39 views

The purpose of the final xor in Davies–Meyer scheme [duplicate]

In Davies–Meyer hash construction scheme each block is xor'ed with the previous block cipher text. Why? The only obvious flaw I see in a scheme without this xor is the possibility to reconstruct a ...
0
votes
0answers
34 views

vector space retrieval model [on hold]

In tf-idf weighting scheme of vector space model, weight matrix is calculated as a product of term frequency(tf) and inverse domain frequency(idf). I need paillier dot product calculation here. Can ...
2
votes
1answer
53 views

Security of DES P_BOX

I'm curious about the design of the P_BOX of DES. I found a paper on this topic, but it dates back to 1989. This means the effect of p-box values of the cipher immunity against Differential ...
1
vote
1answer
71 views

Attacker in a key exchange

I'm having trouble with the following question: $X(A) \rightarrow B:(A,N_X)$ $B \rightarrow X(S):(B,((A,N_X,T_B),K_{BS}),N_B)$ $X(A) \rightarrow B:(((A,N_X,T_B),K_{BS}),(N_B,N_X))$ ...
3
votes
2answers
142 views

Does RSA operate over a Finite Field (Galois Field)?

Is it correct to say that RSA operates over a Finite Field (Galois Field)? In this case GF(p)? I do understant that the modulo in RSA is not itself a prime number, but all the operations ...
13
votes
4answers
310 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 ...
3
votes
1answer
157 views

Can keys from Bitcoin's Hierarchical Deterministic Wallets be correlated (reducing privacy)?

I'm trying to understand if the feature "Hierarchical Deterministic Wallets" in Bitcoin allows for complete privacy of all derived keys, and if any of those keys can be associated with each other ...
2
votes
1answer
52 views

How do we find the subkey out of a differential cryptanalysis?

I understand the differential cryptanalysis up to the "finding the last subkey" part. If XORing with the key doesn't change the differentials, how can testing different key affect the equations we ...
0
votes
0answers
29 views

Memory requirement in light weight block ciphers cryptanalysis

If we have a light weight block cipher where the block length is different than the key length. Let's say the block has a length of 64 bits while the key is 80 bits. For an attack to be successful, ...
1
vote
2answers
148 views

why $e(g,g)^N=1$ in bilinear pairings holds?

I can't get the point of prime order bilinear pairings:$\mathbb{G}\times\mathbb{G}\rightarrow\mathbb{G}_T$,$g=$ generator of $\mathbb{G}$ , $N=p*q$, $p$ and $q$ primes and $e(g,g)^N=1$. why ...
1
vote
2answers
83 views

Group description in pairing based cryptography

Suppose we have a public key encryption scheme, in which public parameter contains $(p, G, G_t, e, g)$, where $p$ is prime number, $G$ is a (cyclic) group of prime order, $e:G \times G \mapsto G_t$. ...
0
votes
0answers
10 views

How does SafeNet MobilePass calculate the counter for following passwords?

Original Question: How does SafeNet MobilePASS generate passwords? The algorithm to calculate passwords was implemented by the author of the original question here: ...
1
vote
1answer
23 views

How does SafeNet MobilePASS generate passwords? (TOTP Variant)

This question is similar to How does SafeNet MobilePASS generate passwords? The question and answer there is related to the HMAC Variant of SafeNet Mobilepass. I'm looking for details on the TOTP ...

15 30 50 per page