0
votes
0answers
3 views

A question about fully homomorphic encryption (FHE)

Hypothesis: We define the messages on a field $\mathtt{F}_p$, where $p$ is a large prime number. I am considering a dynamic outsourced private data scenario. Assume we have 3 messages: $m_1=2, ...
0
votes
0answers
7 views

How the non adjacent form algorithm be implemented in java?

I am looking for implementation of NAF algorithm in Java, but I can't find any source code. ...
2
votes
1answer
12 views

Prove that the following MAC is insecure

I am trying to prove that the following MAC is insecure, but I don't know how to exploit the properties of the pseudorandom function $F$ involved: Gen generates a uniform $k \in \{0, 1\}^n$. To ...
-1
votes
1answer
16 views

Security timestamp

I want to prove the security of a cryptosystem, that makes use of trusted timestamps. Unfortunatelly I can't find any information about how a secure timestamp is defined (I was looking for sth like ...
1
vote
0answers
33 views

Is it possible to enumerate the possible RSA keys?

As far as I understand ECDSA keys are smaller than RSA because all of the value of the ECDSA (up to a high number) are valid private keys. Is there any method of compressing RSA keys, based on some ...
2
votes
0answers
22 views

Statistical tests for PRNG that generates a sequence which is not binary

Is there a pratical application to PRNG that generates a sequence which is not a binary one? A ternary, quaternary sequence, for instance. If so, how can we test this? Is there any alternative test ...
0
votes
1answer
23 views

How is the base64 encoded signature in Craig Wright's proof constructed?

Mr. Craig S. Wright might be Satoshi Nakamoto - the inventor of bitcoin. He is currently proving the case. But how is the base64 encoded proof, that is published by himself on his blog post ...
2
votes
1answer
44 views

ECFP harder than ECDLP ?

Given two points $P$ and $Q = \sum_{i=1}^{n} x_i.P$ over $E_p(a, b)$ for $x_1,x_2,...,x_n \in \mathbb F_p$. The Elliptic Curve Factorization Problem (ECFP) is to find the points ...
0
votes
0answers
27 views

Is their any symmetric key cipher (block or stream cipher) providing partial decryption?

symmetric key cipher (block or stream cipher) providing partial decryption of data at some points. Although the entire data is not been decrypted but the data decrypted to that specific point should ...
0
votes
0answers
9 views

Why does HS1-SIV use the universal hash function the second time?

HS1-SIV uses HS1-Hash twice: once with the message as input, and the second time with the authentication tag as input. The second use seems somewhat strange to me: assuming that the core is a strong ...
0
votes
0answers
11 views

Hash function with good performance on extremely short messages

Are there randomized hash functions that are fast for extremely short messages (usually <10 bytes) and almost universal?
0
votes
0answers
18 views

PHP Apple News HASH HHMAC

I am having a problem generating the signature key in PHP as describred in the Apple nes API documentation found here: ...
-5
votes
0answers
16 views

Here I am like a [on hold]

I don't know if it's the place to ask this, but I realy don't know where to look for this information. I heard someone says "Here I am like a..." And that sentence reminded me of something I have ...
0
votes
0answers
8 views

TLS 1.2 PRF Cipher Suite Specification

I am upgrading our assembler SSL/TLS implementation to support TLS 1.2 and am reviewing RFC5246 specification for TLS 1.2. It states that the PRF is now part of the cipher suite specification but ...
1
vote
0answers
22 views

Algorithm to rotate values in a predefined manner

I will start with an example. Some beacon like estimote Beacons use something called secure ID. The ID transmitted by the beacon change every 10 minutes autonomously without contacting the server. ...
1
vote
2answers
31 views

Converting a 5-bit s-box to its bit-sliced format

I'm currently trying to convert a 5-bit sbox (the one from this cipher: http://primates.ae/wp-content/uploads/primatesv1.02.pdf) to its bit-sliced format (i.e. to a boolean network). Most papers ...
1
vote
1answer
26 views

If I am about to generate one-time pad, where should I generate my pads from?

If I want to generate a few one-time pads, is it OK to just read required number of bytes from /dev/urandom without weakening information-theoretical security?
0
votes
1answer
24 views

Fully or partially Decrypting Data with Multiple keys

Is there any good paper or research carried out till now that a data is encrypted by a single key or onwer(user) and their are 2 or more decryption keys. One key can decrypt the entire data. Other ...
0
votes
0answers
21 views

What kind of analysis can I perform on my implementation of Salsa20 and Rabbit ciphers?

I've implemented both the Salsa20 and Rabbit ciphers in C#. My implementation is for academic purposes and I've tested both of them against the test vectors. I implemented a system that encrypts a ...
1
vote
0answers
47 views

Yaos Millionaire Problem: Why distance >= 2?

I'm currently reading about Yao' Millionaire Problem: http://research.cs.wisc.edu/areas/sec/yao1982-ocr.pdf Alice and Bob want to know which of them is richer. Let $j \in \{1, \cdots 10\}$ be Bobs ...
0
votes
1answer
37 views

tls 1.2 finished message stucture

I am implementing TLS 1.2 and using ECDHE_RSA_AES_128_GCM_SHA256 cipher suit. According to RFC 5246 finished messages have {verify_data[verify_data_length]} and verify_data = PRF(master_secret, ...
3
votes
1answer
23 views

How are the IVs of SHA512/256 and SHA512/224 calculated?

This seems odd to me, because there are a lot of resources out there saying that the initializer values of SHA512 and SHA384 are the first 64 bits of the fractional parts of the square roots of prime ...
7
votes
3answers
105 views

How to prove the security of block ciphers

I see very often proofs of security for asymmetric crypto algorithms, for instance, using reductions to known hard problems, or game based proofs... In the field of protocols (like authentication) it ...
0
votes
0answers
49 views

Which AES encryption do banks use? [on hold]

I'm trying to find what size keys banks use for symmetric and asymmetric encryption. I know that the symmetric one is smaller because they want it to be fast but I can't find any information on their ...
0
votes
0answers
32 views

Weil Pairing - Miller's Algorithm

I'm trying to implement Weil Pairing using Miller's algorithm. I have got couple of questions. How to select $m$? As stated in this link page 13, I interated from $1$ to order of point $P$ such that ...
6
votes
1answer
62 views

Is every point on an elliptic curve of a prime order group a generator?

If the order of elliptic group is prime then every point is a generator of that group. I tested the above statement on some elliptic curves and found it true. Does that really work on all curves? Is ...
1
vote
0answers
37 views

Is 3 rounds more secure than 2 in this simplified DES?

Consider the following simplification of DES: a plaintext message block of $2n$ bits of length is divided into two blocks of length $n$ (left half $L_0$ and right half $L_1$). In other words, the ...
1
vote
1answer
35 views

Triple DES with 2 keys

Suppose triple DES is performed by choosing two keys $K_1$ and $K_2$ and computing $C = T (T (T (L, K_1), K_2), K_2)$. How to attack this modified version with a meet-in-the-middle attack, in which ...
1
vote
1answer
36 views

Is it safe to use fast/small hash for key identity?

I have to roll database access keys often, but it's important to know which key each system is using in order to avoid unavailability. I want the systems to report that without exposing the key ...
0
votes
1answer
44 views

Two Bilinear Pairing in Cryptography

I want to create 2 Bilinear Pairing $e_1$,$e_2$ such that $e_1:G_0 \times G_0 \rightarrow G_1$ and $e_2:G_1 \times G_1 \rightarrow G_T$ and use this to encrypt a message $M$ in the form $M ...
1
vote
0answers
46 views

Is it safe to encrypt data using XOR along with CSPRNG seeded with a truly random number?

I was wondering a couple of days ago whether I could reverse the normal encryption order to produce a good AES based cipher variant. The method is as follows: Two users, Alice and Bob, each have a ...
0
votes
1answer
15 views

Create composite group for pairing in JPBC

We use bilinear map $S = (G, G_T , e(\cdot, \cdot))$ of composite order $n = s \times n'$ with two subgroups $G_s$ and $G_n'$ of $G$. Random generators $w \in G$, $g \in G_s$, and $φ \in G_n'$ are ...
4
votes
2answers
59 views

Strength of $H(k\|H(m))$ as a MAC algorithm

What is the strength of $H(k \| H(m))$ compared to HMAC? Compared to $H(m \| k)$? What is the strength in bits of a given key/output size?
0
votes
0answers
11 views

Can anyone tell whether combinational has higher frequency of operation than sequential or vice-versa?

I have designed SHA3 algorithm in 2 ways - combinational and sequential. The sequential design is giving frequency of operation as 700MHz while the combinational one is giving 0.5MHz so i want to ask ...
3
votes
1answer
29 views

How much does using the same $H$ for all messages weaken GCM?

How much is GCM weakened by using the same MAC key $H = E_K(0^*)$ for all messages that use the same key (which is what GCM actually does) instead of using $E_K(N||0_{32})$ (which is different for ...
21
votes
1answer
3k views

Examples of modern, widely used ciphers that suddenly fell?

RC4 and GOST are two major ciphers (defined as being widely used to encrypt large amounts of data) that fell to cryptanalysis (relatively) suddenly. The first becoming totally broken and the second ...
6
votes
1answer
49 views

How distinct are the meanings of the terms “CSPRNG,” “DRBG” and “stream cipher”?

Are there universal, consensus definitions for the following terms? Cryptographically secure pseudo-random number generator ("CSPRNG") Deterministic random bit generator ("DRBG") Stream cipher ...
0
votes
1answer
72 views

Is double AES-CBC encryption with the same key and IV unsafe?

If some plaintext encrypted twice with the same AES function (CBC-mode), same IV and same key, is it possible to retrieve either the key or the plaintext?
5
votes
1answer
71 views

Why do we use hex output for hash functions?

Why do we use hex representation as default for the output of a hash functions result? For example the sha256 hash function: the output of sha256 in hex representation uses 64 characters, while ...
0
votes
0answers
34 views

1-out-of-2 OT from Random 1-out-of-2 OT

Last week I came upon this problem in my h.w.: Let $OT^m$ denote 1-out-of-2 oblivious transfer of $m$ bit inputs. Let $RandOT^m$ denote the following primitive: The sender’s input ...
0
votes
1answer
30 views

Homomorphic multiplication by a scalar

Few homomorphic encryption schemes like Paillier , Ring-LWE support homomorphic multiplication operation by a scalar apart from additive homomorphic property. Loosely they could be defined as below ...
0
votes
0answers
40 views

Deoxys: disadvantages vs. AES?

The CAESAR candidate Deoxys is based on a tweakable block cipher that seems to be a strict improvement over AES, in that it is a tweakable cipher resistant to related-key attack. The mode proposed ...
0
votes
1answer
51 views

Where is the mistake in my RSA by-hand calculation?

Like several previous askers, I seem to have made a mistake in my RSA calculation, but despite going back over it three times, I cannot spot it. I picked 1000003 and 6000011 as my primes, ...
1
vote
1answer
51 views

Why is DSA falling out of favor?

Windows abandoned DSA rather than extend it to support > 1024 bits; but otherwise I cannot find a reason why DSA would be less desirable. I see in SSH the disabling it by default with a completely ...
0
votes
0answers
10 views

Cryptographic key with editing safeguard [on hold]

I need to encrypt a number in a file, say 142345. It encrypts to EfsFjs or something else. I need a method that safeguards ...
0
votes
0answers
17 views

Is AES-256 bit encryption secure against this kind of attack? [duplicate]

Recently I came across this article. http://www.cs.tau.ac.il/~tromer/acoustic/ Could this put all computers at risk for decryption?
1
vote
1answer
35 views

Can I get successful signature verification with just altering message and signature?

Assuming I can modify a message and also modify the verification signature, and I also have the public-key but not the private-key. Can I create a message that can be verified with a signature that I ...
1
vote
0answers
22 views

Determining an encryption key when ciphertext and algorithm are known

I would like to know how I can tell that I have successfully performed an exhaustive search attack on an encrypted message. Here are the conditions: key is 40 bit I am aware of the cipher text and ...
0
votes
0answers
14 views

What are the advatages or disadvatages of using seperate chaining over linear or quadratic probing?

I was looking through different hash methods the other day and was curious as to what the advantages or disadvantages of using separate chaining over linear or quadratic probing. I know that with ...
4
votes
2answers
627 views

Is this simple PRNG secure?

$G$ is a PRNG used in a stream cipher and defined in the following way: G receives $s_0$ as an input, which is a random string drawn from a uniform distribution. The output of step $i$ is $s_i = ...

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