4
votes
1answer
155 views

Determining if Server/Client's TLS configuration is Vulnerable to SLOTH

In the context of SSL/TLS protocol and SLOTH vulnerability. I want to find out if certain websites(webservers) or applications that use TLS are vulnerable. I need some guidance for this. My idea is ...
3
votes
1answer
163 views

Unable to understand hash function representations

I have some hash function representations, which I find it hard to understand. I have searched a lot but didn't found anything helpful. Please help me understand the hash function representations ...
4
votes
2answers
125 views

Name and security of these non-invertible functions?

I would like to learn more about a specific set of non invertible functions: The function should accept 2 inputs: one hidden and the other visible. The output and the function should also be visible....
0
votes
0answers
29 views

Uniformly distributed sub-sequences of a main PRG sequence

Let $ g_s $ be a pseudo-random generator that generates uniform distributions of numbers ($s$ : seed) of a fixed bit-size. One wants to compare the pseudo-randomness of certain subsets of elements ...
2
votes
2answers
77 views

BOOLEAN FUNCTIONS: generate a function $f: \{0, 1\}^n \rightarrow \{0, 1\}$ from a $n \times n$ S-Box

I want to calculate the hamming weight of a S-Box using this formula: $\text{hw}(f) = \sum_{x=0}^{2^n-1} f(x)$. Where $f: \{0, 1\}^n \rightarrow \{0, 1\}$ My problem is that I don't know how to get ...
6
votes
1answer
50 views

Understanding the definition of HGD

On the section 4.2, page 10, of the paper Order-Preserving Symmetric Encryption, the authors define two subroutines: the first one is called $HGD$ and the second one is $GetCoins$. I have doubts ...
0
votes
0answers
77 views

Semaev summation polynomials

I am little confused how this attack works. We have the points $P, Q$ such that $Q = nP$. We let $u_{1} $and $u_{2}$ such that $R(x,y)=u_{1}P+u_{2}Q$. Then if we find the solution $x_1,...,x_n$ of the ...
1
vote
1answer
52 views

Computing the cardinality of the co-domain of specific modular exponentiations

Consider the following function: $f: \mathbb{Z}_n \rightarrow Y,~x \mapsto x^e \bmod n$, where $n = p \cdot q$ is an RSA modulus and $gcd(\varphi(n),e) \neq 1$ (different as required for a public ...
0
votes
0answers
85 views

Proof that this is not a secure pseudorandom function

$p$ is a large prime number. Consider the following function $F:\mathbb Z^*_p \times \mathbb D\rightarrow\mathbb Z^*_p$ where $\mathbb D=2,....,p-1$. $F_k(x)=x^k \bmod p$ Proof that it's not ...
1
vote
1answer
143 views

Limitations of Elliptic Curve Cryptography?

Simple question, what are the limitations of ECC, both in terms of application and how secure it is? I heard that the NSA were able to read emails a few years back due to a backdoor they had ...
0
votes
0answers
33 views

Using Montgomery ladder to calculate the coordintes

In one of my assignments I need to solve the below: For a Montgomery curve $3v^2 = u^3+u^2+u$ over ${\mathbb{F}}_{11}$ and point $P = (9,8)$. I need to compute $x$ coordinate of $3P$ using ...
2
votes
1answer
84 views

Which ciphers produce random ciphertext?

I already know AES produces a "random" output. 5e4e6440826d6afc4535fbf078455f791159701a9df624ddd4e4dda84523b6a7 Its ciphertext doesn't follow a pattern and is ...
1
vote
0answers
61 views

Proving pseudorandom generators

Can anyone please help me on how to prove or disprove (by counterexample) whether the following function $G'$ is a PRG (Pseudorandom Generator) given that $G$ is a PRG. $$G'(s) = \operatorname{trunc}...
1
vote
4answers
144 views

Is it safe to use XOR to encrypt data key using master key

I am implementing a hierarchical key system with a randomly generated master key and many randomly generated data keys that should be encrypted using the master key. I am wondering what the best way ...
1
vote
1answer
50 views

Is this a secure keyed hashing construction?

I need a PRF for use with PBKDF2, however, the only thing I have is the AES block cipher primitive. I'm attempting to derive a keyed hash function from the block cipher. The design is based on the ...
11
votes
10answers
3k views

Are there any advantages in using proprietary encryption?

Proprietary software generally relies on the fact that in keeping the encryption algorithm private, it gets an extra layer of security implying "Security through Obscurity." Obviously this phrase has ...
3
votes
0answers
65 views

Why reveal MAC-keys after using them?

As far as my understanding goes MACs are used to determine whether the received message comes from a source that has access to a MAC-key which is known by both parties. Some crypto protocols reveal ...
1
vote
0answers
42 views

Algebraic relationship between Original Key and Sub Key of DES

Does there exist any sorts of algebraic relationship between Original and Sub Key of DES? I understand that by solving K-Maps of 64-bit Input/48-bit Output, I can get 16 algebraic relationships ...
3
votes
1answer
128 views

Practical attack on an impractical implementation of Rijndael (AES?)

My understanding of the cryptanalysis of AES, is based on what I've read on Wikipedia and my intuition, I have nothing but self-taught education on the subject. So I want you to imagine: I have only ...
7
votes
5answers
306 views

Does frequent key change weaken encryption?

Following scenario: We are using OTR for communication between Alice and Bob which means after each successfull message exchange a re-keying happens for both parties leading to new AES-keys for the ...
1
vote
1answer
102 views

Encrypting and Authenticating The Simplex Communication Between Embedded Devices

I am planning to build temperature sensor nodes for my home heater control. Central device will control the heater using temperature data read by nodes. These nodes will send temperature data to ...
3
votes
1answer
110 views

Why gcd(r,(p-1)/r) needs to be 1 in benaloh cryptosystem

I recently discovered the benaloh cryptosystem. I am working with the system as it is discribed in the following link: https://en.wikipedia.org/wiki/Benaloh_cryptosystem However I need some help in ...
1
vote
2answers
41 views

Are there any disadvantages of using libsodiums helpers for en-/decoding/comparision instead of the native ones?

Libsodium has some helpers, which allow hexdecimal decoding, encoding and also constant-time string comparison. So if you use the php binding libsodium-php you ...
0
votes
3answers
62 views

Defining Symmetric vs Asymmetric cryptosystems

I'm writing a project on the advantages and disadvantages of symmetric vs asymmetric cryptosystems. At the moment I am trying to define both systems using mathematical notation. Under the heading "...
1
vote
0answers
60 views

Encryption technology for DARPA

I'm working on a short story taking place in the near future in which a hacker gains access to the DARPA mainframe and files related to a highly classified DARPA project. Being ignorant about state ...
3
votes
1answer
79 views

4 x E = D in Simplified AES how it's possible?

Can anyone explain how it's possible through hexadecimal or Binary 4 x E= D
2
votes
1answer
76 views

Does the time to evaluate a hash function depend on the function input size?

Suppose we have a (variable-input size) hash function modeled as a random oracle. Can it be consistent to say that the time to evaluate this function depends on the input size ?
5
votes
1answer
136 views

Can somebody help me understand RC4 Spritz? (Three Questions)

So ever since I first took a stab at understanding stream Ciphers, not one stood out more than RC4, because it's so fantastically simple. As most people reading this will know, with its fantastic ...
7
votes
2answers
123 views

Instantiating a random oracle

I am studying about RO model and just got this question that what are the factors that make it not possible to instantiate a RO with a Hash function. To give a reference on how far I know about them ...
1
vote
0answers
113 views

Example of FHEI scheme?

I am reading this paper Toward Secure Multikeyword Top-k Retrieval over Encrypted Cloud Data. I am trying to work out an example of the FHEI (Fully homomorphic Encryption over Integers) scheme ...
4
votes
3answers
134 views

Proof of non-membership on a merkle tree

Assume a user U and a server S. User uploads its data and wants later to perform an authenticity check. It also sends a merklee tree to the server. Lets say we would like the user to ask for a ...
5
votes
1answer
309 views

Affine Cipher over an Affine cipher

I would like to know your view about the title, encrypting a plain text with an affine cipher then encrypting that ciphertext once more using the same cipher, but of course different keys. Would it be ...
-1
votes
1answer
264 views

Should I use RSA encryption since RSA is said to be broken by NSA? [closed]

I am developing a simple web app that uses asymmetric encryption, but I am not sure whether to chose RSA for the reasons mentioned above. What are your suggestions? Also if I decided to go with RSA ...
3
votes
2answers
72 views

Are low security curves for ECDSA not supported?

I am working in a very bandwidth restricted environment, and we are looking to implement ECDSA digital signatures. Although they are no longer recommended, we might be looking to use curves that are ...
3
votes
1answer
81 views

Containers for secret key

What 'container' is used normally to store/transport secret keys (for symmetric algorithms)? I have come across PKCS12 format where a public key certificate as well as a private key can be bundled ...
7
votes
1answer
694 views

What is difference between meet in the middle attack and man in the middle attack?

From my understanding man-in-the middle attack works as follow: Alice and Bob agreed to use Diffie-Hellman using $a$ and $q$. Alice sends $Y_A$. Before it reaches Bob, Charlie ...
1
vote
1answer
454 views

Difference between AES CMAC and AES HMAC?

Can someone elaborate on how 'signing' is done using AES- CMAC and AES-HMAC? HMAC Signing as I understand: Compute the HMAC( Hash the key and the input concatenated in a special way) Verification: ...
6
votes
1answer
117 views

Generating a key to use with AES

I'm going paperless, and I want to encrypt the documents that I scan. I'd like to use CommonCrypto to perform AES-XTS encryption on each file. I'm a software engineer, and I like the idea of being ...
3
votes
1answer
159 views

Can a book cipher be cracked without key?

Book cipher works this way : Choose a reference book. For each word find its position in the book. replace each word by its coordinates (ie: 2,3,4 = page 2, 3rd line, 4th word). How would ...
2
votes
0answers
81 views

Can we break ECDLP with this machine?

Let $P$ and $Q$ are two points of NIST elliptic curve $E$ (defined over $F_{2^m}$ with prime $m$) and $k$ is a private key such that $k.P=Q$. Also we have a machine that is able to leak some ...
1
vote
1answer
195 views

Simplied DES why 10-bit key?

In Simplified DES algorithm, the plain text is 8-bit & the key is 10-bit, why is that, why can't both be of 8-bits each?
3
votes
1answer
70 views

Faster alternative to HKDF

HKDF is used in one of my projects to derive separate keys from a common master key. But profiling has shown it to be the performance bottleneck under certain circumstances. Is there any faster ...
1
vote
0answers
16 views

References for cascade [closed]

I have found many sources against cascading encryption, however I am having trouble finding arguments FOR using cascading. AES-256 + BlowFish + RC5 etc... each with a different key. This is for ...
0
votes
0answers
15 views

Are the ECDSA public keys of a stable/fixed length relative to curve size? [duplicate]

I am working in an environment with strict bandwidth requirements, and we need predictable bit lengths of the stuff we send. We need to broadcast ECDSA public keys, and we are using OpenSSL to ...
2
votes
1answer
95 views

Can I shorten the large ECDSA public key output file from OpenSSL?

I am working in a very bandwidth restricted environment where I from time to time have the need to distribute public keys. The distribution happens in bit format, so there is no need for encoding, at ...
3
votes
2answers
155 views

Understanding the length b used in MD5

I am trying to understand MD5 hash algorithm from the link http://www.ietf.org/rfc/rfc1321.txt At first I was not able to understand padding of MD5. Then I asked a question in this link: To ...
2
votes
0answers
43 views

What is the canonical way of creating merkle tree branches?

I'm currently looking into creating some compact merkle tree branches to prove that a given hash was included in a given merkle root. My initial thought was to list the leaf, the merkle root and all ...
-3
votes
1answer
52 views

1 bit shannon entropy CPU instructions?

It has been proved, that the xor operator is suitable for entropy accumulation, due to its theoretical shannon entropy of 1 bit. There are six truth tables with ...
3
votes
1answer
60 views

Does a “commutative” asymmetric system exist?

Completely crypto noob here. I'm looking for a cryptosystem made of a func f + key1 + key2 such that they satisfy: g(f(msg, key1),key2)=msg g(f(msg, key2),key1)=msg key1 != key2 Does such a ...
4
votes
0answers
47 views

Security parameter p =O(n)

In many homomorphic encryption scheme, a security parameter is calculated as p =O(n). How to use the complexity order as values? Is there any specific method with an appropriate example?

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