0
votes
2answers
126 views

Sending the next one-time pad key in this one-time pad message? [duplicate]

I am doing a research project on cryptography next year, and I'm really new to cryptography. This isn't some really advanced thing or anything, and I'm just trying to come up with something basic. ...
0
votes
2answers
1k views

AES-CTR in BouncyCastle with string key, without IV or salt [closed]

Our team is encrypting data using a javascript snippet. My problem is I'm supposed to parse them back in my Java code. I am having troubles identifying parts of the algorithm. The code says it's CTR ...
0
votes
1answer
428 views

How was the MDS matrix used in AES chosen?

$$\begin{pmatrix}2&3&1&1\\ 1&2&3&1\\ 1&1&2&3\\ 3&1&1&2\end{pmatrix}$$ In the above MDS matrix used in AES encryption, why are the numbers $2$,$3$ and $1$...
0
votes
1answer
55 views

Interesting malleability property of Goldwasser-Micali PKC

GM is a cryptosystem with a modulus $N = pq$ ($p$, $q$ prime) and quadratic nonresidue $r \in (\Bbb Z / N\Bbb Z)^*$ as the public key. You can see the details on Wikipedia. Anyway, let's say that $N &...
0
votes
1answer
262 views

Why using AES in ECB (Electronic Code Book) mode a bad idea? [duplicate]

Why using AES in ECB (Electronic Code Book) mode a bad idea? is CTR mode better? Given only these two can be used for parallelization.
0
votes
1answer
77 views

Authenticating small packets

I intend to authenticate small packets of data, between 16 and 256 bytes each. For some of them encryption will also be required. This will be used on small micro controllers, with RAM sizes ranging ...
0
votes
1answer
66 views

Constructing set membership proof for private set

Is it possible to construct a set membership proof to show $\delta \in \Psi$ where $\delta$ is publicly known and $\Psi$ should stay only known to the prover? It seems rather impossible but I would ...
0
votes
1answer
54 views

Can you identify this algorithm? [closed]

We are attempting to integrate our application in to a third party system. To do this we need to pass encrypted passwords in to this system. I have decompiled the assembly and looking at the code it ...
0
votes
4answers
179 views

One time pad in CBC mode?

I have been searching about if it is more secure to use CBC mode in OTP but I can't find anywhere where people have sad that it is more secure. Question: Is CBC mode in OTP more secure? Because I ...
0
votes
1answer
84 views

What is the difference between H(M) and H3(M, s, IDA)? [closed]

What is the difference between H(M) and H3(M, s, IDA)? I am aware of Hash function with a Message and a Key, but there are three parameters in: H3(M, s, IDA). Here M is the message, s is the key, ...
0
votes
1answer
60 views

Executing encrypted code? [closed]

I want a code 'black box' that receives data inputs, processes those inputs, then sends out the outputs. I want the code to be encrypted, or somehow obfuscated. Is there any known way to do achieve ...
0
votes
1answer
122 views

Huffman encoding of hashes

I have a huge list of MD5 hashes, which takes up quite some space. I was wondering if I would acheive (some) compression, by encoding the characters (which are A-F 0-9), with huffman coding. I made a ...
0
votes
1answer
38 views

HTTPS and plaintext authentication

I have client connecting a server over HTTPS to send and retrieve data. The client always connects through HTTPS The certificate is known to the client beforehand (hard coded into the software) The ...
0
votes
1answer
295 views

Why exactly Blowfish max key length is 448

Could anyone, please, tell me history of birth of Blowfish algorithm? Specifically, what is substantiation of Blowfish key length to be in range from 32 till 448 bits? Why, for example, it wasn't 64-...
0
votes
1answer
93 views

How to perform homomorphic multiplication in ElGamal?

How can I compute homomorphic multiplication in ElGamal? That is: Given two ciphertexts $(R_1,c_1)$ and $(R_2,c_2)$ corresponding to plaintexts $m_1$ and $m_2$ under some public key; how can I compute ...
0
votes
1answer
139 views

Has a collision ever been found for SHA-1/2/3 when truncated to 128 bits?

I'm aware that MD5 is broken, and collisions have been found for it. I'm interested in other hashes (SHA-1, SHA-2, SHA-3) when truncated to the same digest size, i.e. 128 bits. The time complexity of ...
0
votes
1answer
33 views

Strenght of TLS handshake

I asked this question recently but I was told it is not save to simply send over the identifier for your crypto method you want to use. for example, say the server has crypto method 3 5 and 6, the ...
0
votes
1answer
132 views

Rsa Key Exchange Protocol

Moderators: Maybe this question will be move to other sub-forum. My question is Anybody know some link with a tutorial of how implement the RSA key exchange protocol using java for chat comunication?
0
votes
1answer
629 views

Why cant Public Key Encryption be perfectly secure? [duplicate]

I would be very grateful for any help. I cant figure out why (probabilistic) public key encryption schemes can never provide perfect secrecy? Any Ideas? Excerpt: In contrast to the private-key ...
0
votes
1answer
144 views

how does an initialization vector work? [duplicate]

Can somebody please explain how an initialization vector works. My current understanding is that it is used to prevent 2 of the same messages looking identical after encryption, but isn't this the ...
0
votes
1answer
79 views

Segmenting encryption to get the same results with the same key

The given examples below are dummy and in English. They are mainly for place holding as this is a concept question rather specific example based Given AES has a block size of 128 bit (16 letters of ...
0
votes
1answer
128 views

RSA: How to calculate the private exponent?

I have this problem: In RSA algorithm considering $n=33$ (modulus) and public exponent $e=3$, calculate the corresponding private exponent $d$. I know that $d = e^{-1} \pmod{\varphi(n)}$ and $\varphi(...
0
votes
1answer
245 views

Encrypt file name

I'm looking to encrypt (rename) mutiple files name based on a passphrase. Currently the passphrase would be numeric but I can change that to something else if required. I would like to be able to ...
0
votes
1answer
334 views

Where can I learn the basics of AES?

I was tasked with making an expo about AES and its steps, but I still can't grasp it, especially when it comes to "key schedule". Does anyone know some good material to start learning? Or can someone ...
0
votes
1answer
81 views

How to select a 'tweak' used in FE1 mode format preserving encryption?

I'm experimenting with this library Botan which includes a module for format preserving encryption based on FE1 mode. The parameters for the Encrypt method are as follows ...
0
votes
1answer
65 views

Decrypting DES - limited information

I have a list of DES encrypted strings/data, they come in two lengths, 32 chars hex (16 bytes) or - I believe - 64 chars. I know the key, which is 8 ascii chars (I might add that I am the rightful ...
0
votes
1answer
41 views

What is the signifcance of inside threat in “How to Construct Multicast Cryptosystems … Secure Against CCA2”

In How to Construct Multicast Cryptosystems Provably Secure Against Adaptive Chosen Ciphertext Attack, the paper states under preliminaries: We consider the scenario where a single party, called ...
0
votes
1answer
61 views

Deterministic outputs based on non-connected inputs

I am looking for a one way function that can generate outputs deterministically. However, revealing any of the inputs dont allow the person to generate other inputs. E.g: lets say we have a list of ...
0
votes
1answer
279 views

Super-simple encryption of short strings

I want to anonymise the initials of experiment participants by giving each a pseudonymic set of initials, by encrypting their true initials. Their initials are only two or three letters in length. ...
0
votes
2answers
209 views

Are there drawbacks to encrypting data locally before being encrypted in cloud backup (multiple encryption)?

I am planning on backing up my hard drive using a cloud backup service but have become skeptical of the industry based on incidents like these: http://dbmsmusings.blogspot.com/2011/02/why-i-no-longer-...
0
votes
1answer
138 views

Using HMAC SHA256 to protect payment files in local trusted network

in a project that I am working on we have been tasked with eliminating PGP while providing sufficient security to protect payment files only within the Company's trusted network. We arrived at HMAC ...
0
votes
1answer
90 views

Knowing N and a relationship between the 2 prime numbers(p and q) find p and q generated with RSA

Let there be $p$ and $q$, 2 prime numbers for which the following relationship is true: $|p-q| < 2 \cdot N^{1/4}$. The algorithm first generates the prime number $p$, then it generates $q$ close ...
0
votes
1answer
275 views

Multiple AES/ECB encryptions of different data with same key all end with same pattern

We have used "AES/ECB/PKCS5Padding" with a 256 bit key. We encrypt different streams of data (blockwise) with the same key. Each encrypted stream ends with same pattern. What is the reason for this?
0
votes
1answer
67 views

Why perfect secrecy can be ensured when a plain message and a cipher-text based on one-time pad are correlated?

First, some well-known results are as follows. For random variables $X$ and $Y$, we have $$H(X,Y) \leq H(X) + H(Y).$$ The equality is achieved when $X$ and $Y$ are independent. Second, in one-time ...
0
votes
1answer
93 views

What is the meaning of h(r) in this protocol?

Could somebody tell me what the meaning is of $h(r)$ in the protocol below? ‎‎$A‎\leftarrow‎{B}\quad:{h(r)‎‎}{,B}{,P{_A(r,B)}}‎ \\A‎\rightarrow‎{B}\quad:r$
0
votes
1answer
88 views

How much of Probability do I need to know to study Cryptography?

I have just started MSc in Computer Security. I didn't study probability before. Now, I have some short time to complete my MSc semester. What are the minimum topics from 'Probability' do I need to ...
0
votes
1answer
79 views

How to encrypt a vector $e\in Z^{m}$ using LWE

I have a vector $e \in Z^{m}$, now I want to encrypt it by using LWE (Learning With Errors). Because in LWE, we have to encrypt of a bit $\{0,1\}$. How can I encrypt a vector $e \in Z^{m}$? Thank you ...
0
votes
1answer
102 views

Randomness in generation of Virtual Machines from pre-built Image [closed]

I am studying Multi-Tenancy vs. Virtualization, and I got thinking about randomness, true randomness, virtualization etc, and I couldn't find anything on it. From what I gather, ...
0
votes
1answer
352 views

Affine transformation in AES: Matrix representation

I know that the affine transformation of the AES can be represented both as a polynomial evaluation over $\operatorname{GF}(2^8)$ and as a matrix-vector multiplication (see, e.g., p.212 C.4 of The ...
0
votes
1answer
92 views

New to cryptology, studying key exchange

I'm just getting an overview of some of the concepts in key exchanging at the moment, and I'm a bit disoriented on a few topics, namely key stretching, key derivation functions and perfect forward ...
0
votes
1answer
349 views

uniform vs. non-uniform PPT

I'm trying to understand PPT and in particular what the differences are in uniform and non-uniform PPT's. First, this is how I see it: A Probabilistic Polynomial-Time algorithm A is an algorithm that ...
0
votes
1answer
81 views

RSA weak padding

Suppose to have a function for numbers expressed in 8-bit $\in [0,2^8-1]$ defined as: $$f(x)=x||x||x||x$$ where $|f(x)|$ is exactly 32 bits. e.g., suppose x=2 (00000010) so $f(x)=2+2^9+2^{17}+2^{25}=...
0
votes
1answer
81 views

RSA Decryption from samples

I am working on a project for a client which involves decryption of data which was encrypted using RSA. The system in question retains three independent copies of each data-set, but each copy is ...
0
votes
1answer
564 views

How do you break encryption on a message? [closed]

This may seem like a simple question, but I have just started studying cryptography and I can't seem to find any information on this at all. I am trying to write a "simple" encrypted messenger using ...
0
votes
1answer
29 views

Reordering of multiple signed blocks

I would like to refer you to page 430 of the Handbook of Applied Crypto, where the authors said "... reordering of multiple signed blocks presents a security risk..." This statement was made in ...
0
votes
1answer
68 views

Workaround to implementing Forward Secrecy

In the case where I am self-signing my digital certificates, if I just change my certificate (generate a new one) every week or month, will this have (sort of similar to) the same effect as ...
0
votes
3answers
139 views

Key length requirement in a simple XOR implementation

I don't have much previous experience at all with cryptography, this is pretty much the first time I've tried anything similar. I'm trying to implement an extremely simple XOR encryption system in ...
0
votes
1answer
190 views

Keeping the key and IV safe when AES256 encrypting publicly known data

I am encrypting some publicly known data, and some private data using the same key, using AES256 with CBC. An attacker does not have the ability to choose what the public data is. Is this safe? (It ...
0
votes
2answers
86 views

Find the prime factorization in the DLP

Suppose we have $g^x \equiv h \pmod N$ Where $N = pq$ and $p$, $q$ are distinct primes. Also $(p-1)/2$ and $(q-1)/2$ are primes. If we know what $x$, $g$ and $h$ are, is it possible for us to know ...
0
votes
1answer
221 views

How to compare between two cryptographic algorithms in terms of security? [closed]

How to compare between two cryptographic algorithms (e.g. SHA-1 and SipHash) in terms of security? That is, how could one prove that algorithm X is more secure than algorithm Y?

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