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47 views

Another cut-and-paste attack on CBC mode

I am trying to see specific cases of attacks in the CBC mode, in particular, I am investigating some attacks such as Example of a cut-and-paste attack on CBC. Here I have posted something similar and ...
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0answers
34 views

Confidential data encryption on ethereum

I already built a supply chain that is able to collect product information on Ethereum. Now, that data can be confidential, but I still want to do Matrix calculations on it. I came across homomorphic ...
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1answer
117 views

PKCS12 password of container and private key

As I understand pkcs12 defines a container structure that can hold both a certificate and one or more private keys. ...
0
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1answer
80 views

Why mining bitcoins is difficult?

As I understand to obtain a Golden Block is to finding a nonce that matches a hash lower than a given target, as shown in this research-gate article. And here is a "py" kernel: Bitcoin mining python (...
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2answers
80 views

Relationship between $N$ and $\phi(N)$ in the RSA algorithm

Recently I started learning how the RSA algorithm works and there is one single part of the computation which really confuses me and can't get over it. Let's say I chose 2 prime numbers, namely $P ...
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0answers
16 views

Are the receivers in stateless broadcast encryption assumed to be computationally bounded?

I started to read about the broadcast encryption problem, specifically, the first, seminal work of FN93 followed by the subset cover technique presented at NNL01, and something really trivial and ...
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1answer
45 views

Could randomisation make for a better book cipher?

Suppose that the file linux.words is used as the "book". This is a publicly available list of just shy of half a million words. And suppose that this book is used, not in its native alphabetic order,...
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0answers
35 views

Are there any state of the art crypanalysis tools for stream cipher

I am new to cryptanalysis and interested in knowing cryptanalysis tools (black boxing or white boxing) for (not any specific) stream ciphers in general sense. Scenario: I am given an assignment to ...
3
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1answer
299 views

What does “crypto_box” actually mean in libsodium and NaCl?

I cannot find what "crypto_box" actually means. In general, and in specific cases, what does "box" do? I know that libsodium is authenticated encryption, but GPG is not. "Box" makes me think the ...
6
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2answers
431 views

Where did ChaCha20 and Salsa20 stream ciphers get their names from?

This is not a question targeted at a specific crypto implementation, but a question out of curiosity. What's the reason for calling the stream ciphers ChaCha/Salsa? I couldn't find any information ...
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1answer
48 views

Prime computation for Diffie Hellman

While reading some cryptographic RFCs, came across the Diffie Hellman prime computation formula: 2^1024 - 2^960 - 1 + 2^64 * { [2^894 pi] + 129093 } I am curious what the expression [2^894 pi] means ...
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2answers
68 views

If we don't trust current PQ algorithms enough to use them on their own why should we trust them for a hybrid?

The second question my students have asked me about PQ/Classical Hybrids is about why we think they are good for protecting information with a long security lifetime. If we don't trust current PQ ...
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1answer
55 views

Are PQ/Classical Hybrid Key Exchanges a reflection of how little we trust PQ cryptography primitives?

My students have asked me some questions about why there are standards being developed for hybrid public key systems with both a classical and a post-quantum component. Given that when elliptic ...
4
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1answer
108 views

Using Diffie–Hellman without a key derivation function

In an answer to another question, it was suggested that the shared secret derived from Diffie–Hellman key exchange could then be used directly as a one-time pad to encrypt a message (by XORing the ...
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0answers
49 views

How decode works in CCA1 scheme based on MP12 construction?

In Section 6.3 from MP12 we have that $encode(m) = Sm$, for $S$ any basis of $\Lambda(G^t)$. Then I have: $S = \begin{pmatrix} 1 & 2 & 4 & 8 & 16 & 32 & 64 & 128 & 256\...
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1answer
45 views

Meaning of difference Δ delta

I tried to understand some crypto text but I am new to this. Does this: Let $X,X'$ be $\ell$-bit values, and $\Delta X=X\oplus X'$ means that $X$ and $X'$ have $\ell$ bits and $\Delta X=X-X'$ or ...
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332 views

RSA. Would someone kindly help me understand what d and c are in this factorization exercise?

What are $d$ and $c$ in this factorization exercise? What order must $d$ and $c$ have for $p$ and $N$? If $N=pq$, $(p+q-4) =0 \bmod 8$, and $p \geq (p+q)/4$ $$N=66390187$$ $$(3*N-1)/8=24896320$$ ...
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1answer
95 views

How to decrypt using CRT, and then verify by encrypting without CRT?

Here is the actual question that I need to answer: An RSA encryption scheme has the set-up parameters $p = 31$ and $q = 37$. The public exponent is $e = 17$. Decrypt the ciphertext $y = 2$ using the ...
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2answers
95 views

A doubt about Diffie-Hellman Key Exchange

I have a doubt about the Diffie-Hellman problem: Is it possible to send a message to someone using only the Diffie–Hellman key exchange? Since it's called a key exchange can you only make a key?
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1answer
62 views

RSA Decryption: Doubts: knowing p or $\phi(n)$ can lead to find private exponent?

I have some doubts about RSA (the public key $n$ and $e$ is public): Note $n = pq$ and $\phi (n) = (p-1)(q-1)$ 1) Say if some hacker knew $p$, why would it be easy for them to find $q, \phi (n), d$? ...
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0answers
32 views

Does fixing partial bits of a SHA256 hash increase the probability of finding a preimage using the meet-in-the-middle attack?

Let’s say I want to find a partial rather than full preimage using the meet-in-the-middle attack. For example, my goal is to find a preimage so that the first 76-bit output of the hash are all ...
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2answers
50 views

Is the order of applying transformations in SP cryptosystems significant?

SP-cryptosystems Is the order of applying transformations in SP cryptosystems matter? What will change if we first apply the P-transformation and then the S-transformation? Will cryptographic strength ...
1
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1answer
31 views

Are the signcryption and the authenticated encryption same?

The signcryption and the authenticated encryption are both the combine of encryption and authentication with three natural composition (i.e., EtS, StE, E&S). I am not sure that if they are the ...
2
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1answer
79 views

Murder Mystery Party

For a "Murder Mystery Party", one person is chosen anonymously to be the murderer (i.e., only the murderer knows who the murderer is) by shuffling cards with everyone randomly taking a private card (...
1
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1answer
51 views

Can I make fixed-length ciphertext with AES-256-GCM?

I have a question about AES-256-GCM encryption. Can I make a fixed-length encryption output? In my understanding, I cannot make a fixed-length ciphertext. To me, the fixed-length output is much more ...
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0answers
30 views

Norms in differential privacy

I know that perturbation should be proportional to the $\text{L}_1$-sensitivity of the function if someone wants ($\epsilon,0$)-differential privacy, and proportional to the $\text{L}_2$-sensitivity ...
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0answers
9 views

cryptojs TDES convert to OPENSSL [migrated]

I write this code in nodejs for decrypt 459508BB6B65C5A304D3EFB133038A14 with TripleDES: <...
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0answers
46 views

Google Timeline: is it encrypted and if so who has the key? [closed]

Google Timeline claims (e.g. here) that "Your Timeline is private, so only you can see it." What does that mean? As a cryptographer I would take that to mean that the Timeline data is encrypted using ...
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1answer
50 views

Simple: Hash Into a Prime Field

If I have some bytes, and I want to compute a secure hash into a prime field which is 300 bits long I can: Use a nice hash, like sha3_512, and then modulo my prime field (introduces some bias). ...
2
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1answer
32 views

How can an adversary use Mac(.) with a new key to compute a tag although this is not a query to Mac oracle?

I am having some troubles understanding the power of an adversary in attack against a MAC. In chapter 4 in Introduction of Modern Cryptography by Jonathan Katz and Yehuda Lindell, specifically in the ...
3
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1answer
88 views

Can the knowledge of the inverse of $p$ modulo $q$ help factor $n=pq$? [duplicate]

With the RSA algorithm implemented using the Chinese Remainder Theorem (CRT), the private key has to be provided with not only $p$, $q$ and the private exponent $d$, but often also with the pre-...
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1answer
54 views

Decisional Discrete Logarithm problem?

Has the decisional version of the discrete logarithm problem been studied somewhere? I mean, for known $G$ in a group, distinguishing $xG$ and $Y$ for unknown integer $x$ and group element $Y$?
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2answers
109 views

Sigma protocol with Pedersen commitment and Hash function

Suppose I construct a Pedersen commitment as $g^m h^r$. I could pick the randomness in a "pseudo-random" fashion, such that $r = H(m)$. My questions are as follows: Given that $H$ is collision-...
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0answers
27 views

Probabilistic Symmetric Key Generation

Here is a brief description: We have two parties, Alice and Bob. Each party must choose either a positive key or a negative key. Subsequently, Alice will generate a 0 or a 1 at random and send it to ...
2
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1answer
48 views

How slow is the hash used for Mac FileVault encryption?

Certain password strength estimators (for instance, zxcvbn) give estimates that vary with the speed of the hash and the assumed resources of the attacker. I am curious what hash is used by the MacOS ...
0
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1answer
69 views

Is it hard to find a big random easy to factor number?

Suppose that I give you the challenge of successfully factoring any very big random number. That is, you pick a big random number (say, 65536 bits) and try to factor it. If you manage to, you win. If ...
3
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1answer
57 views

Can the input to a one way function be pseudorandom?

I know that normally a one-way function takes in a completely random input, but can a one-way function take in something pseudorandom instead of completely random? Will it still be a one-way function? ...
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0answers
15 views

Least knowledge ephemeral PKI?

I'm trying to build a PKI for document signing but only using 2nd party auth and no client persistence. I'm assuming I'd need to use something like a SCrypt key of the user credentials for the user'...
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0answers
40 views

Time for brute forcing a substitution cypher with a pentium processor

I am facing the following challenge and have to find an answer by tomorrow. How many days/years/centuries does it approximately take to perform a brute force attack against a sub-stitution cipher ...
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0answers
58 views

What does a repeated byte between two XORed hexadecimal ciphers mean?

I have two different hexadecimal strings (of same length) that I think are encoded plain text strings. Out of curiosity I XORed them and I found a single hex byte repeated for the length of the two ...
0
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1answer
21 views

Is the “decapsulate” function from lattice based cryptography homomorphic?

Observing the code example from pqcrypto-kyber, is the decapsulate function $d$ homomorphic? If $d(ct, sk_i) = ss_i$, is it true that $d(ct, \sum_i sk_i) = \sum_i ss_i$ ?
0
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1answer
42 views

Message input format for RSA algorithm

I was trying to implement the RSA algorithm myself. I have written the key generation part. My question is if I have the word "apple" which I want to encrypt, do I have to convert each alphabet to ...
1
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1answer
33 views

What is a “set synchronized CSPRNG”?

I'm looking to implement a performant revocation method for JWTs. I'm reading a paper, in which the following section's second paragraph states: If we use the client hashing approach described ...
3
votes
1answer
29 views

A problem about Gaussian distribution in paper GPV08

These are contents from the paper Trapdoors for Hard Lattices and New Cryptographic Constructions(GPV08). I do not know the reason about the last sentence. Why these two distributions D_{\Lambda, s, c}...
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1answer
31 views

Dieharder input file with a sequence of only binary numbers

I have a RNG producing sequences of binary numbers, ad I would like to run Dieharder test using them as an ascii txt input file. However I haven't been able to do it properly. Should I use a header ...
2
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1answer
133 views

Why does the one-time pad not imply $P \not= NP$?

I apologize that this is a rather trivial question, but I haven't been able to find an answer anywhere. If the one-time pad is unconditionally secure and impossible to crack (with just ciphertext), ...
1
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1answer
75 views

How to generate a nonce for ChaCha20 Poly1305?

I am using a self implementation of ChaCha20 with Poly1305. Since the nonce is only 96 bits it cannot be chosen at random. Can anyone suggest an efficient method to generate nonce from the key ?
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2answers
123 views

How to securely store and validate a 4-digit PIN used on a mobile device?

I want to be able to securely (1) create and (2) validate a PIN, typed by a user primarily in a mobile app. There is no 'typical' password, although there is another 2nd factor. The starting point ...
3
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1answer
72 views

How to break CBC cipher with partly known plaintext?

I'm learning some IT security and during practice I found an exercise I couldn't solve. I have an encrypted message with block cipher in CBC mode. The blocks are one byte long and the first block is ...
1
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1answer
58 views

Using AES-GCM (or AEAD ciphers in general) as a pure MAC without encryption

What's the opinion on using an AEAD cipher such as AES-GCM for example as a pure message authentication code (MAC) when only message authentication but not encryption is required. does it bring any ...

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