5
votes
2answers
166 views

Should HMAC-SHA3 be preferred over H(C(k,M))?

If I understand correctly SHA-3 (Keccak) is resistant against more attacks than SHA-2. This would make it possible - again if I understand correctly - to use SHA-3 with a simpler scheme than HMAC. ...
0
votes
0answers
39 views

MD5 - Length extension

I am currently trying to get a working understanding of MD5 length extension. I have been following the first exercise located here: https://www.cis.upenn.edu/~cis331/proj1.pdf (it looks like the ...
-1
votes
0answers
10 views

Charm-Crypto: Got <terminated, exit value: 139> when trying to serialize object [migrated]

I'm implementing a Dabe scheme with Charm and I need to share the public parameters over multiple entities. I'm trying to serialize the charm object containing these parameters using objectToBytes() ...
0
votes
1answer
522 views

Are there attacks on AES with 16-bit keys? [closed]

Are there known attacks on AES that uses a 16-bit key? Assuming the data can be 95MB size, and that I can request the same data over and over. For example, can someone explain to me how this code ...
1
vote
2answers
27 views

Validating subset of a password

Is anyone aware of an algorithm/method that allows me to validate just a few letters (or other characters) from a password. For example, the application asks for the 2nd, 3rd, 6th and 9th letters from ...
5
votes
2answers
134 views

Why do cryptographic hashing and symmetric encryption use different functions?

Something about encryption and hashing has always bothered me. Given a cryptographically secure hash function $H$, I can produce an arbitrarily long key from any seed $s$ by recursively applying $H$ ...
1
vote
1answer
46 views

Book recommendation about MPC? [closed]

I have hard time finding introductory book talking about details of secure multiple party computation. Is there any recommendations? Thanks for the help. Hope this is not off topic.
5
votes
1answer
42 views

In Fortuna, can I use ChaCha20 instead of a block cipher and Blake2b instead of iterated SHA256?

In the Fortuna CSPRNG, can I use ChaCha20 instead of a block cipher and Blake2b instead of double SHA256, and still retain security? My hypothesis is "yes" because: The block cipher's only use is ...
0
votes
2answers
39 views

Encrypting using “Cryptography.HMACSHA1”, how to decrypt (VBA)

I have an encryption routine that works very well in VBA. But now I need to program the decryption routine, and I'm stuck. For encryption I'm using HMACSHA1 and transferring the encrypted byte to base ...
-1
votes
0answers
36 views

Encryption program help

First I must say that I don't know which coding language is best for creating an encryption program. But I have an idea for an open source encryption program that uses the program itself to encrypt or ...
4
votes
1answer
31 views

Why ssh-gen makes difference between PEM and PKCS8?

Correct me if I am wrong, but PKCS8 is format to store private key info. It could be binary-enoded (DER) or Base64 encoded ...
-2
votes
1answer
84 views

Decrypting an RSA message given $a^2 \equiv 1 \pmod n$

I need help with a practice problem for an upcoming test. I've learned the answer to the problem is "well done", but don't know how to get there. Any help is greatly appreciated. Suppose that the ...
2
votes
1answer
56 views

SipHash's (non-)collision resistance

I'm very new to cryptography, and I need help understanding the security claims made in Aumasson and Bernstein's paper on the SipHash. In particular, I'm trying to understand the following statement ...
1
vote
0answers
32 views

Does a password that's cracked someone's account increase the chances of cracking someone else's account?

For every find in password that cracks someone's account, does that particular password have a higher probability of cracking someone else's account more than a brute force dictionary choice? How ...
-1
votes
0answers
25 views

Symmetric Cipher Providing full and partial decryption

Let us have Video Data $D$ and we want to encrypt the data in such a way that upon decryption we have multiple decryption keys which will give us full or either partial decryption depending on the ...
5
votes
2answers
151 views

Should RSA primes p and q differ in length by “a few digits”?

When generating RSA keys in the original RSA paper it is stated: to gain additional protection against sophisticated factoring algorithms, p and q should differ in length by a few digits Why is ...
0
votes
0answers
16 views

Securely register a client in server using AES an RSA

I've designed the following protocol to send the client's public key to the server. Initially, the client knows server's public key, but the server does not know the client's public key. client ...
0
votes
1answer
29 views

How to use the hardcoded server's public key to register a client application?

I'm designing the security for a smartphone app that can be used to make car reservations. Clients have to register them with their driver's licence through the application and can then book a car. ...
3
votes
1answer
51 views

What is the branch number of this matrix?

We have the following matrix: $$\begin{pmatrix}0&1&1&1\\ 1&0&1&1\\ 1&1&0&1\\ 1&1&1&0\end{pmatrix}$$ What is the branch number? Is this a MDS marix?
1
vote
3answers
58 views

How to generate many passwords from one passphrase, so that knowledge of one password does not compromise the others?

The limitations are: it should be a function. passphrase is so weak, that if hash of it is known (or big part of hash), then it can be brute forced. I want to get N passwords from one passphrase. ...
1
vote
1answer
54 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, ...
4
votes
1answer
49 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
vote
0answers
54 views

Is it possible to enumerate the possible RSA keys? [duplicate]

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 ...
4
votes
1answer
67 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 ...
1
vote
1answer
46 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 ...
3
votes
1answer
69 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
42 views

Is there any symmetric key cipher (block or stream cipher) providing partial decryption? [duplicate]

symmetric key cipher (block or stream cipher) providing partial decryption of data at some points. Although the entire data has not been decrypted, the data decrypted to that specific point should be ...
0
votes
0answers
13 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
39 views

Hash function with good performance on extremely short messages

Are there randomized almost universal hashes that are fast for extremely short messages (usually <10 bytes)? Edit: This is for hash tables, so it only needs to be hard enough to break to make the ...
0
votes
0answers
19 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: ...
0
votes
0answers
23 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
28 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
50 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
39 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
29 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
1answer
34 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 ...
3
votes
0answers
117 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 ...
1
vote
1answer
108 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
38 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 ...
8
votes
3answers
155 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
39 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
90 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
55 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
46 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
39 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 ...
1
vote
1answer
71 views

Multilinear Pairing in Cryptography

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

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

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
21 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
64 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 ...

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